JP2004510277A - Manufacturing method and authentication method of card on which digital information is printed using digital watermark technology, and their devices - Google Patents

Abstract

To produce a card printed with digital information, a digital image printed on the card is produced using information provided by an applicant requesting issuance of the card, or has authentication information. It is produced using the issuance information extracted from the database. At the same time, a watermark is generated using the authentication information, the watermark is embedded in the digital image, and the watermarked digital image is printed on the card. Thus, the watermarked area is captured from a digital image generated by scanning the printed image, and the watermark is extracted from the digital image within the watermarked area. The watermark is generated by inputting authentication information obtained from the card holder, and the authentication is determined from a correlation between the extracted watermark and the generated watermark.

Description

【００３２】
数１において、ｓは元の信号値であり、ｔは変換された信号値であり、Ｎは信号の長さを示し、係数ｃは下記の数２のように定義される。
【００３３】
【数２】

【００３４】
（但し、１≦ｋ≦Ｎ−１の場合である）。
また、正方行列に対する２次元ＤＣＴ変換は、下記の数３のように定義される。
【００３５】
【数３】

【００３６】
前記数３において、Ｎ、ｓ、ｔは、１次元ＤＣＴ変換におけると同意義であり、ｃ（ｉ，ｊ）は、下記の数４のように定義される。
【００３７】
【数４】

【００３８】
（但し、ｉ≠０、ｊ≠０の場合である）。
また、ＤＣＴ変換は逆変換を有し、１次元及び２次元に対しそれぞれ下記の数５及び数６のように定義される。
【００３９】
【数５】

【００４０】
【数６】

【００４１】
次に、ＤＷＴ変換について説明する。フーリエ変換が正弦関数と余弦関数を基底関数として用いる変換であれば、ウェーブレット変換は基底関数としてウェーブレットを用いる変換であって、連続ウェーブレット変換及び離散ウェーブレット変換に大別される。連続ウェーブレット変換は、下記の数７のように表される。
【数７】

【００４２】
前記数７において、ｓはスケーリングを、τは位置移動（ｔｒａｎｓｌａｔｉｏｎ）を示し、Ψ（ｓ，ｔ）はスケーリングされて位置移動された形態のウェーブレットをそれぞれ示す。
【００４３】
スケーリングは、周波数と関連し、低いスケーリング、即ち圧縮されたウェーブレットは高周波成分を抽出し、高いスケーリング、即ち拡張されたウェーブレットは低周波成分を抽出する。通常、連続ウェーブレット変換は、変換により得られるウェーブレット係数が、スケーリングと位置移動の関数として無限に得られるため、実際の具現が不可能である。
【００４４】
従って、スケーリングと位置移動に対し一定の周波数領域のみを選択する離散ウェーブレット変換を用いると、より効果的に具現することができる。しかし、離散ウェーブレット変換もまた、コンピュータで具現するには多大な演算量による負担が伴われるので、高速ウェーブレット変換であるフィルターバンクを用いて画像イメージを変換させることが好ましい。この方法は、古典的な２チャネルサブバンドコーディング及びピラミッドアルゴリズムを用い、逆変換のためのフィルターバンク間の関係（ＰＲ−ＱＭＦ：Ｐｅｒｆｅｃｔｌｙ ｒｅｃｏｎｓｔｒｕｃｔｉｏｎ ｑｕａｄｒａｔｕｒｅ ｍｉｒｒｏｒ ｆｉｌｔｅｒ）さえ成立すれば、簡単に具現することができるという長所がある。
【００４５】
前記透かし生成部４０は、カード情報データベース２０から所定のユーザキーが入力され、ユーザキーから透かしを生成する。ユーザキーを透かしに用いると、検出した透かしとユーザキーから生成した透かしとの間の相関関係により、デジタル画像の真偽や変更の有無をより正確に判断することができ、透かしの保安性を強化させるという長所がある。
【００４６】
また、ユーザキーから透かしとして用いられる疑似乱数を発生させる前に、ユーザが暗号化器４１を用いて該ユーザキーを暗号化した後、この暗号化したキーを入力され、疑似乱数生成器４２により疑似乱数を発生させる。ユーザキーが暗号化ステップを経ると、ユーザキー値が容易に変形されないだけでなく、ユーザキーそのものを隠匿することができるので、暗号化したユーザキーから生成した透かしをデジタル画像に埋め込むと、その後、デジタル画像から透かしを検出するときにユーザキーそのものが公開される恐れがないという長所がある。暗号化は、通常の暗号化方式、例えば、ＤＥＳ（ｄａｔａ ｅｎｃｒｙｐｔｉｏｎ ｓｔａｎｄａｒｄ）方式、ＲＳＡ方式、ＥＣＣ方式等を用いることができる。本発明では、暗号化するデータがコーディングされ、その結果が疑似乱数（ｐｓｅｕｄｏ ｒａｎｄｏｍ ｎｕｍｂｅｒ）として出力される、ＰＮ−ｃｏｄｅ方式を用いている。
【００４７】
このようにして透かしが生成すると、透かし埋込器１３０により、下記の数学数５による方式のプロセスを経てデジタル画像に埋め込まれる（ステップＳ２３０_１またはＳ２３０_２）。
【００４８】
【数８】

【００４９】
ここで、ｆｘは、デジタル画像に埋め込まれる透かしの強度を調整するための特性関数である。ｆｘは、多様に設定することができ、デジタル画像の周波数領域変換係数（ＦＯＩ）の一部をモジュロ（ｍｏｄｕｌｏ）演算しまたは多数の変換係数の平均、標準偏差、分散等の統計的特性値を取り出す関数であってもよい。
【００５０】
ＦＯＩ’は、デジタル画像の周波数領域変換係数（ＦＯＩ）に特性関数ｆｘを適用した値に透かし（Ｗ）が掛けられた結果を示す。数５における変換係数（ＦＯＩ）は、デジタル画像の周波数領域の値であるため、２次元配列の形態であり、透かし（Ｗ）は、１次元順列（ｓｅｑｕｅｎｃｅ）の形態を有するため、変換係数（ＦＯＩ）を順列の形態にし、または透かし（Ｗ）を２次元ブロック化して演算する。演算のために、画像の周波数係数毎に一つの透かしをマッチングして計算することもでき、複数の画像の周波数係数の統計的な特性を得て、一つの透かしと演算する方法がある。
【００５１】
次に、数８を参考して、透かしが埋め込まれるステップについて詳述する。
前記透かし埋込器１３０は、所定の特定周波数領域の変換係数（以下、埋込係数という）の絶対値に特性関数ｆｘを適用して得た値と透かしを掛けた結果（ＦＯＩ’、以下、代置係数という）を、他の所定の特定周波数領域の変換係数と代置（ｒｅｐｌａｃｅｍｅｎｔ）するプロセスを行う。例えば、デジタル画像を低周波数と中間周波数と高周波数との領域に分けたとき、デジタル画像の情報が相対的に少なく含まれた中間周波数領域または高周波数領域に透かしを埋め込むことになり、低周波数領域の変換係数（埋込係数）に特性関数ｆｘを適用した値に透かしを掛けた結果（代置係数）で、既存の中間周波数領域や高周波数領域の変換係数を代置することにより、透かしの埋込みが完了する。
【００５２】
このような方式によると、高周波数部分の一部を捨てる圧縮ステップやぼかし（ｂｌｕｒｒｉｎｇ）のような変形があったとしても、透かしは、低周波数領域の係数と掛けられて高周波数領域に代置されるものであり、変形後も高周波数領域が相当部分残るようになるため、変形に強いという長所がある。
【００５３】
本明細書では、透かしが、低周波数領域の係数の絶対値に特性関数ｆｘを適用した結果と掛けられ、中間周波数領域と高周波数領域の間に代置されることを一例として示しているが、デジタル画像の品質を低下させない範囲の周波数領域を選択して透かしを埋め込こんでもよい。例えば、高周波領域の変換係数の絶対値に特性関数を適用した結果に透かしを掛けた後、高周波数領域に代置することができるので、周波数領域に変換されたデジタル画像に透かしを埋め込む方法はこれに限らず、多様な周波数領域においても応用され得る。
【００５４】
また、本発明は、印刷により画像の全体的な特徴があまり変わらない点に着目し、任意の周波数領域の係数で他の周波数領域の係数を補償することにより、画像の全体的な特性に変化を与えないとの周波数領域の特性を用いれば、印刷に強い特徴を有するようになるので、印刷等により透かしが消えてしまうことを防止することができる。また、上述した周波数領域の特性を用いた透かしの埋込法によると、透かしを埋め込んでもデジタル画像の全体的な特性が変わらないため、即ちデジタル画像の原本の品質が低下しないため、印刷後にもデジタル画像の原本の品質を鑑賞することができる。
【００５５】
数８において、デジタル画像に透かしが埋め込まれたとき、透かしの強度の強さを調整するものはｆｘ関数である。この特性関数値は、ユーザが任意に設定することができるので、いかなる値も可能であり、特に透かし（Ｗ）の埋込みによるデジタル画像の品質が低下しないように適切な関数で決定することができる。即ち、透かしの強度の強さとデジタル画像の品質の変形は、互いに反比例の関係であるため、透かしの使用環境とデジタル画像の品質維持の側面とを考慮して決めることが好ましい。
【００５６】
次に、透かしが埋め込まれたデジタル画像を得るため、逆周波数領域変換器１４０は、周波数領域に変換されたデジタル画像を復元させる（ステップＳ２４０_１またはＳ２４０_２）。前記周波数領域変換器１２０がＤＣＴ変換やＤＷＴ変換またはＦＦＴ変換を用いた場合、逆周波数領域変換器１４０は、逆ＤＣＴ変換や逆ＤＷＴ変換または逆ＦＦＴ変換を用いる。ここで、デジタル画像がカラー画像である場合は、逆カラーモデル変換器１５０により、逆周波数領域変換が行われた輝度成分と、周波数領域変換が行われなかった輝度成分を除いた残りの成分を用い、ＨＳＢモード、ＹＩＱモードまたはＹＣｂＣｒモードのカラーモデルから元のカラーモデルに復元される（ステップＳ２４５）。最後に、透かしが埋め込まれたデジタル画像を得ることにより、透かしのデジタル画像への埋込みプロセスが終了する（ステップＳ２５０）。
【００５７】
このようにして、デジタル画像に対する透かしの埋込みステップが終了すると、カードの原資材にデジタル画像印刷部６０からカードの表面に印刷して透かしが埋め込まれたカードを製作することができる。
【００５８】
このように製作された本発明による透かしが埋め込まれたカードにおいて、埋め込まれた透かしは位置や内容により多様に決められ得る。透かしの内容が文字や数字またはイメージであるか、または透かしが埋め込まれる位置がカードの全体または一部であるかは、カード製作／発給者が選択する透かし技法の特徴により多様に決められる。例えば、上述した透かしが埋め込まれたカードの製作ステップにおいて、透かしを埋め込む部分がカード発給者の写真である場合、先ず、写真が印刷される所定の空間を空白として残し、写真の他にカードに印刷される情報のみをカードの原資材に印刷してから、カード発給申請者の写真をデジタル画像で製作し、このデジタル画像にのみ透かしを埋め込んだ後、透かしが埋め込まれたデジタル画像をカードの原資材の所定の位置に印刷してもよい。これに対し、透かしを埋め込む部分がカード全体であれば、カードに印刷される情報をカードの原資材全体のサイズと同一のサイズのデジタル画像に製作した後、このデジタル画像に透かしを埋め込んでから、カードの原資材に印刷してもよい。または、透かしがカードに印刷されるイメージの特定の部分に埋め込まれる場合は、透かしが埋め込まれる部分に特定の識別子を表示する方法を用いてもよい。
【００５９】
以下、図５乃至図８を参照して、このような製作ステップを経て作られた透かしが埋め込まれたカードに対する認証のための装置とその方法について説明する。透かしが埋め込まれたカードを認証するステップ及び装置は、上述したカードの製作ステップ及びその装置に対応するように構成され、透かしが埋め込まれたカードを認証するステップで用いられる透かしの検出技法は、透かしが埋め込まれたカードの製作ステップで用いられる透かしの埋込技法に対応する。
【００６０】
図５は、図１におけるカード製作装置により製作されたカードを認証するためのカード認証装置の構成を示すブロック図である。図５におけるカード認証装置２００は、ユーザキーを入力されて透かしを生成する部分と、カードそのものに記録された情報を処理する部分に大別される。カードそのものに記録された情報とは、カードの表面に印刷されたデジタル情報に含まれた透かしとマグネチック線を用いて記録されたカードユーザ情報を含む。前記カード認証装置２００は、カード認証者がカードの認証だけでなく、個人身元情報やカードの内訳のような情報も共に確認できるようにデータベースと連動する構造にしてもよいが、カードの認証のみを行う装置の場合は、別途のカード情報データベースを含まない。
【００６１】
前記カード認証装置２００は、カードに含まれている情報を認識するためのカード認識部２１０と、ユーザキーを入力するためのキー入力部２２０と、カード認識部２１０から抽出されたデータを用いて該当ユーザのカードに対する情報を検索して抽出するデータベース検索情報抽出部２３０と、前記抽出された情報のうち、カード認証者が所望の情報を抽出するカード情報データベース部２４０と、カード認識部２１０から認識されるカードのデジタル画像の抽出等の処理ステップを行うデジタル画像データ処理部２５０と、抽出したデジタル画像とキー入力部２２０から入力されたユーザキーに基づいて生成する透かしを用いて認証を行う透かし認証サーバ２６０と、認証の結果を出力する結果出力部３００とを備えている。
【００６２】
以下、図６を参照して、このような構成を有するカード認証装置２００における各構成部材の動作と共に全体の動作ステップについて説明する。
【００６３】
カード認証者は、カードの偽変造の有無及びカード所持者の真偽を確認するために、カード所持者に、透かしが埋め込まれたカードの認証装置のカード認識部２１０にカードを入れてキー値をキー入力部２２０から入力させる（ステップＳ３００）。前記カード認識部２１０は、カード所持者が入れたカードからカードシリアルナンバーやカードユーザＩＤ等の読み取られた種々のカード情報をデータベース検索情報抽出部２３０に伝送する一方、カードに印刷されたイメージを走査し、カードに印刷されたイメージをデジタル画像データのフォーマットでデジタル画像データ処理部２５０に伝送する。
【００６４】
前記データベース検索情報抽出部２３０は、カード認識部２１０から伝送された種々のカード情報のうち、カード所持者の身元情報や取引きの内訳等、カード認証者が所望の情報を抽出するための検索情報（カードシリアルナンバーやユーザＩＤ等）を抽出して、カード情報データベース部２４０へ送る。検索情報の抽出は、カードに貼り付けられているマグネチック線とバーコードのように情報記録と表示の機能を行う要素に記録されている部分により行われる。前記カード情報データベース部２４０は、データベース検索情報抽出部２３０からの検索情報を用いてカード認証者が所望する所定のカードユーザに関する情報を抽出し、抽出した情報を結果出力部３００に伝送して、カードユーザ情報を得るステップを終了する（ステップＳ３４０〜Ｓ３６０）。
【００６５】
また、前記デジタル画像データ処理部２５０は、上述した透かしが埋め込まれたカードの製作時、透かしを埋め込んだデジタル画像領域に対応する領域内のイメージのみをキャプチャーして透かし認証サーバ２６０に伝送する。キャプチャーする領域内のイメージのサイズは、カードのサイズの範囲内であればよく、特に限定されるのではない。このとき、カード面に印刷されたイメージから透かしを検出するためには、透かしが埋め込まれた位置を知らなければならないので、透かしを埋め込むステップにおいて、透かしの埋込領域を予め決めておくと、透かし検出の際には、その領域に対応する位置のイメージのみを得ればよい。或いは、透かしを埋め込むとき、埋込領域を表示する別途の識別子を埋め込んだ場合は、該識別子を探索して探し出した後、該識別子により決められる領域内のイメージのみをキャプチャーする。透かし認証サーバ２６０に高速伝送するために、透かしが埋め込まれたイメージデータを圧縮してもよい。
【００６６】
前記透かし認証サーバ２６０は、キャプチャーしたイメージデータから透かしを検出する（ステップＳ３１０）。透かしの検出は、埋め込んだときに適用した透かし技法に対応する検出方法を用いる。検出した透かしとユーザキーにより生成する透かしを比較し（ステップＳ３２０）、比較結果による認証の結果をカード認証者が確認できる所定の形式に出力して、透かしの検出及び認証のステップを終了する（ステップＳ３３０）。このような機能を行う透かし認証サーバ２６０は、周波数領域への変換及び周波数領域係数を用いて透かしの検出を行う透かし検出部２７０と、ユーザが入力したキーを暗号化した後、暗号化されたキーを用いて透かしを生成する透かし生成部２９０と、透かし検出部２７０で検出した透かしと透かし生成部２９０で生成した透かしとの相関関係により認証の有無を決定する比較演算部２８０とを備えている。
【００６７】
以下、図７及び図８を参照して、透かしの検出方法について説明する。
前記透かし認証サーバ２６０の透かし検出部２７０は、デジタル画像データ処理部２５０からの透かし埋込みイメージを伝送され、本発明の検出方法に従い透かしを検出する。若し、デジタル画像データ処理部２５０においてイメージデータを圧縮した場合は、透かし検出部２７０は、これに対応してイメージデータの圧縮を解いた後に透かしを検出する。
【００６８】
また、カード所持者は、カード認証装置２００のキー入力部２２０にキー値を入力する。キー入力部２２０は、カード所持者から入力されたキー値をデジタル化したデータとして透かし認証サーバ２６０へ伝送する。透かし認証サーバ２６０の透かし生成部２９０は、透かし埋込時と同一の方法により、キー入力部２２０から伝送されたキーデータを暗号化し、暗号化したキーデータを用いて透かしを生成する。
【００６９】
次いで、比較演算部２８０は、透かし検出部２７０で検出した透かしと透かし生成部２９０で生成した透かしとの間の相関関係から認証の有無を決定し、その認証結果を結果出力部３００へ伝送する。
【００７０】
最後に、結果出力部３００は、カード情報データベース部２４０から抽出された、カード認証者が所望する所定の情報及び透かし認証サーバ２６０の比較演算部２８０から伝送された認証結果を、カード認証者が確認することができる形態に出力する。
【００７１】
前記ステップのうち、カード認識部２１０からカードが入れられたか否かが確認されると、カードの認証とカード所持者の真偽を判別するための透かし検出及び認証ステップ（ステップＳ３１０〜Ｓ３３０）と、カード認証者が必要とするカードユーザの情報をデータベースから検索して抽出するためのステップ（ステップＳ３４０〜Ｓ３６０）がそれぞれ行われる。二つのステップは互いに独立したプロセスであるため、二つのステップを平行して行うことが、処理時間を短縮することができるので好ましい。
【００７２】
以下、図７及び図８を参照して、本発明によるカード製作装置において用いられた透かし埋込方法と関連し、透かしを検出して認証するステップについて詳述する。
【００７３】
図７は、図５における透かし認証サーバの構成を具体的に示す詳細ブロック図であり、図８は、図７における構成によるカードの透かしの比較ステップを示すフローチャートである。
【００７４】
図７における透かし認証サーバを構成する各ブロックは、上述した透かし埋込部における構成部材と同一であるので、それぞれの機能についての説明は省略し、全体的な動作を記述する。
【００７５】
前記デジタル画像データ処理部２５０により処理された透かしが埋め込まれたデジタル画像が、白黒／カラー画像判別器４１０に入力される（ステップＳ４００）。この白黒／カラー画像判別器４１０は、透かしが埋め込まれたデジタル画像が白黒画像であるかカラー画像であるかを判別する（ステップＳ４１０）。透かしが埋め込まれたデジタル画像が白黒画像であると、周波数領域変換器４３０により輝度成分に対する周波数領域変換が行われ（ステップＳ４２０）、カラー画像であると、先にカラーモデル変換器４２０によりＨＳＢモード、ＹＩＱモードまたはＹＣｂＣｒモード等のカラーモデルに変換される（ステップＳ４３０）。周波数領域変換器４３０により輝度成分に対してＤＣＴ変換、ＤＷＴ変換、ＦＦＴ変換の周波数領域変換が行われる。
【００７６】
このようにして、透かしが埋め込まれたデジタル画像に対し、周波数領域変換後に得られる変換係数からデジタル画像に埋め込まれていた透かしを検出し、元の透かしを復元する（ステップＳ４５０）。透かしの検出は、所定の特定周波数領域の係数に特性関数を適用した結果に透かしを掛けて、他の所定の特定周波数領域の係数に埋め込むプロセスの逆プロセスを行うことであり、透かしが埋め込まれたデジタル画像から、上述した特定周波数領域に埋め込まれている代置係数（ＦＯＩ’）と、代置係数（ＦＯＩ’）の計算に用いられている埋込係数（ＦＯＩ）を求め、その埋込係数及び代置係数を用いて透かしを復元する。
【００７７】
また、透かし生成部２９０は、ユーザキーを入力され、ユーザキー暗号化器４４０により透かし埋込みステップと同様の方法で暗号化し、擬似乱数生成器４５０によりＰＮ−ｃｏｄｅ方式による透かし（Ｗ）を生成することになる。透かしの生成は、ユーザキーから透かしを生成する方法以外に、例えば、所定の保存媒体に予め保存されていた幾つかの透かしのうち、いずれか一つの透かしを埋込み及び検出する例もあり得る。このようにユーザキーが入力されていない場合は、埋込係数と代置係数から求めた透かしを、例えば予め保存されている幾つかの透かしと比較して、所定の透かしが埋め込まれているか否かを判断することができる。
このようにして、復元された透かし（ＷＥ）と、透かし埋込時に使用された方法により生成した透かし（Ｗ）との間の相関関係を分析することにより、デジタル画像に所定の透かしがあるか否かを検出することができる（ステップＳ４６０）。ところが、透かしが任意のサイズ値を有する順列である場合は、透かしを復元するために埋込係数と代置係数の値を使用しなければならず、例えば、透かしが１と−１のみを有する二進数列である場合は、特性関数ｆｘの値が常に正数であるとの仮定下で、代置係数の符号のみでも透かしの値を復元することができる。
【００７８】
前記比較演算部２８０で行われる相関関係の分析は、検出された透かし（ＷＥ）とユーザから入力されたキーを使用して生成した透かし（Ｗ）との相関関係及びその相関値を求め、ユーザが指定した透かしが埋め込まれたことを確認することにより、透かし認証装置２００で検査されるデジタル画像の真偽、変更の有無が分かる。
【００７９】
以下、透かし（ＷＥとＷ）間の相関関係及びその相関値を求める方法について説明する。透かし（ＷＥとＷ）間の相関関係は、下記の数９により求められる。
【００８０】
【数９】

【００８１】
ここで、
【００８２】
【数１０】

【００８３】
はＦＦＴ（Ｗ）の共役複素数を示し、ＩＦＦＴ（Ｗ）は逆ＦＦＴ（Ｗ）を示す。上記数９から求められた相関関係の結果は、ある一つの値でなく、シーケンスの形態Ｘ_１…Ｘ_Ｎであるので、求められた複数個の値Ｘ_１〜Ｘ_Ｎを比較して最大ピーク値Ｍ及びその位置Ｐを求める。その後、数９から求められた相関関係の結果から、尖度、即ち４次モーメント（Ｋｕｒｔｏｓｉｓ）Ｋを次の数１１によって求める。
【００８４】
【数１１】

【００８５】
ここで、Ｘ_１…Ｘ_Ｎは上述のように数９から得られる数列であって、透かし（ＷとＷＥ）間の相関関係の結果値であり、
【００８６】
【数１２】

【００８７】
はＸ_１…Ｘ_Ｎの平均を、σは標準偏差を示す。
【００８８】
このように求められた相関値Ｋ、Ｍ、Ｐを分析すると、所定のユーザキーで生成した透かし（Ｗ）と検出した透かし（ＷＥ）が一致するか否かを判別することができる。詳しく説明すると、相関値Ｋ、即ち尖度（Ｋｕｒｔｏｓｉｓ）が所定のしきい値未満であれば透かし（ＷとＷＥ）が一致しないことを示し、最大ピーク値Ｍが所定のしきい値未満である場合も、透かし（ＷとＷＥ）が一致しないことを示す。また、透かし（ＷとＷＥ）の最大ピーク値の位置Ｐが常に同一である場合にのみ透かし（ＷとＷＥ）が一致することを意味する。
【００８９】
また、透かし生成部で生成した擬似乱数は、自己の信号以外の擬似乱数とは相関度が‘０’であるので、擬似乱数による相関度もまた、所定のしきい値以上である場合は、透かし（ＷとＷＥ）が一致することを意味する。従って、デジタル画像が上述した相関値の条件を全て満たしていると、透かし（ＷとＷＥ）が一致することを意味するので、デジタル画像の認証を確定することができることになる。
【００９０】
産業上の利用可能性
以上のように、本発明によると、クレジットカード、ＩＣカード、スマートカード、学生証、社員証、カードキーのようなカードに加えられ得る不法行為を防止すると共に、このようなカードが偽変造された場合を容易に検出することができ、カードとカード所持者の真偽を確認／決定する認証効果を得ることができる。特に、データベースシステムと連動すれば、カードの真偽の認証以外にも身元情報を同時に把握することができる。また、磁性体との接触等に影響されず、取扱性も良好である。
【００９１】
以上、本発明による透かしが埋め込まれたカードの製作方法及び認証方法、並びにそれらの装置についてその好ましい実施の形態を開示してこれを例示により説明したが、これは、この技術の分野における熟練者にとって、このような実施の形態は単に例示のためのものであって、これに限定されるものではなく、本発明の技術的思想の範囲内で種々に変更または変形され、置き換えられることは明白である。
また、本発明の技術的思想は、上述した実施の形態に限定されず、添付の特許請求の範囲及びそれと同等の技術的原理によってのみ限定されるものである。
【図面の簡単な説明】
【図１】本発明による一実施の形態の電子透かしが埋め込まれたカードの製作装置の概略構成を示すブロック図である。
【図２】図１におけるカード製作装置による透かしが埋め込まれたカードの製作ステップを説明するフローチャートである。
【図３】図１における透かし関連構成を具体的に示す詳細ブロック図である。
【図４】図３における構成により透かしが埋め込まれたデジタル画像の製作ステップを示すフローチャートである。
【図５】図１におけるカード製作装置により製作されたカードを認証するためのカード認証装置の構成を示すブロック図である。
【図６】図５におけるカード認証装置でのカード認証ステップを示すフローチャートである。
【図７】図５における透かし認証サーバの構成を具体的に示す詳細ブロック図である。
【図８】図７における構成によるカードの透かしの比較ステップを示すフローチャートである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a card on which digital information is printed using an electronic watermarking technique, an authentication method, and an apparatus therefor. More specifically, the contents printed at the time of manufacturing a card on which information is printed are digital information. The present invention relates to a method for manufacturing and an authentication method for a card printed with digital information formed by embedding a watermark that cannot be identified by the naked eye and a device thereof.
[0002]
[Prior art]
Conventionally, in order to prove your identity and qualification, do you include ID information such as ID card such as resident registration card, passport, student card, employee card, driver's license, qualification card, credit card, card key, etc. Alternatively, various cards for proving / confirming the identity are widely used. However, in spite of the importance of the information contained in such cards, the fact is that the number of cases where cards are illegally falsified and used is increasing.
[0003]
In order to solve such a problem, the following methods have been conventionally proposed and used.
[0004]
First, there is a method in which a photo is pasted and coated on printing paper on which identity information and the like are printed. This is currently used in passports and the like. However, such a method simply authenticates the card and the holder if the photo of the card and the owner match, so after removing the coated paper and replacing the photo, it is necessary to finish it properly There was a problem that it could be easily changed.
Second, there is a barcode method, which is a coding system for expressing information in an arrangement pattern of black bars and white bars having various widths. If an identification card is manufactured by pasting or printing a barcode, the authenticity of the identification card, the identity information, and the authenticity of the holder can be confirmed based on the information read from the barcode reader at the time of entry and exit. However, since barcodes are easy to duplicate, barcodes with the same pattern may be imitated and used illegally. There is a lot of room to be done. In addition, the bar code cannot be read by a bar code reader in many cases, and a keyboard must be provided for this purpose.
[0005]
Third, there is a magnetic line on which predetermined information is recorded magnetically. Most credit cards attach a magnetic line to the back of the card, record the information on this magnetic line, and Adopt a way to provide minimal information on
[0006]
[Problems to be solved by the invention]
However, in the case of such a method, when a magnetically strong object is touched, the information recorded on the magnetic line is easily damaged, and the information recorded on the magnetic line is easy to read. There is a problem.
[0007]
Furthermore, the method of determining the authenticity of the card holder is roughly classified into two methods.One is to make a distinction with the naked eye by using a photograph, and the other is to make a distinction using a personal identification number. It is. However, the method using a photograph is not only meaningless as a discriminating method in a situation where forgery and falsification is easy as described above, but also discriminating by comparing a card holder with a photograph attached or printed on a card one by one. Is inferior in discriminating power due to time constraints and the like.
[0008]
The method of comparing the cardholder's PIN with the actual PIN is currently the most widely used discrimination method, but since the PIN is generally made up of four-digit Arabic numerals, anyone with an unlawful intent can be identified. Cheap. Although it is possible to maintain security from a third party by frequently updating the personal identification number, it has a disadvantage that it is extremely complicated to go through the updating procedure again or to create and store a new personal identification number. . Of course, both the visual discrimination method using a photograph and the password number comparison method can be used, but even if the two methods are performed in parallel, the above-mentioned problems cannot be solved clearly.
[0009]
Needless to say, recently, in order to solve such a problem, a method of digitizing and printing information recorded on a card may be adopted. However, in such digitization, the technology itself can be copied without limitation without damaging the original, and since it is difficult to distinguish the duplicate from the original, illegal duplication and illegal distribution are performed indiscriminately. That is the fact.
[0010]
These methods are currently applied to prevent illegal use due to forgery or the like of the card, but are identifiable with the naked eye, the recorded information is easy to read out, easy to change, and concealable There are various problems, such as the amount of information is extremely weak, easily damaged, and time-limited. Due to such limitations of the prior art, despite their importance, there is a risk that the card will be used illegally.
[0011]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and digital information is printed using a digital watermark technology that prevents a forgery or falsification of a card by embedding a watermark that cannot be identified with the naked eye in a printed digital image. It is an object of the present invention to provide a card, a method of manufacturing the card, and an authentication method and device.
[0012]
It is another object of the present invention to provide a card which can be printed with a watermark embedded therein while minimizing deterioration of the quality of digital information printed on the card, and a method and apparatus for manufacturing the card.
[0013]
Further, the present invention embeds a watermark in the digital information to be printed by using the frequency domain characteristic, so that the quality of the digital information is not degraded, and the preservability of the watermark against the deformation of the image printed on the card. It is still another object of the present invention to provide a card on which digital information having high and strong characteristics is printed, and a method of manufacturing and authenticating the card.
[0014]
In order to achieve the above object, a card manufacturing apparatus in which information for authentication according to the present invention is embedded, means for storing card issuing information and card authentication information of a card issuing applicant, and the storing means Means for converting the card issuing information into a digital image having a shape of a predetermined size, setting the card authentication information of the storage means with a user key, and generating a watermark using the user key; The digital camera further comprises means for embedding the watermark in a digital image, and means for printing the digital image in which the watermark is embedded on a raw material of a card.
[0015]
According to the present invention, there is provided a card authentication device in which information for authentication is embedded, a means for scanning an image printed on the card to generate a digital image, and inputting card authentication information from a card holder. Means for determining the presence or absence of authentication by calculating a correlation between a watermark generated using the card authentication information input from the card holder and a watermark detected from the digital image. It is characterized by having.
[0016]
The method performed by such an apparatus can be configured in the same manner.
When a card is manufactured in this way, it can be prevented from being changed by embedding a watermark that cannot be identified with the naked eye. Also, when the key determined by the true card holder is generated as a watermark, the watermark detected from the card and the key input from the card holder are used when authenticating the card or determining the authenticity of the card holder. And whether or not they match, it is possible to determine whether the card has been changed or not, and whether the card holder is authentic. Further, the content of the concealable information can be diversified, and the position where the information can be concealed can be arbitrarily selected. In addition, the watermark itself is not liable to be damaged, and it is difficult to change the watermark. Furthermore, accurate and quick inspection can be performed by detecting and comparing the watermark using a computer.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, a general card issuing process will be described. The card issuer provides the card producer / issuer with the identity information (eg, name, resident registration number, address, bank account number, etc.) and information required for card issuance, such as photos. At this time, the card issuance applicant determines the key value and provides it to the card producer / issuer. This key is character or numeric information such as a personal identification number, an employee number, or various IDs. The card producer / issuer saves the information, including the key, provided by the card issuer in the database, and extracts from the database only the information to be printed on the card material among the information from the card issuer. . Thereafter, using a general card production graphic tool, a digital image including information to be printed on the card material extracted from the database is produced. The digital image produced by using a general card production printer is printed on the material of the card, thereby completing the card production and issuing the card to the card issuing applicant.
[0018]
In the present invention, the card manufacturing step further includes a step of generating a watermark using a key provided by the card issuance applicant, and then embedding the watermark in a digital image printed on the raw material of the card. The key can be concealed to make it difficult to imitate or duplicate the card, thereby preventing forgery and falsification of the card. Also, by detecting a concealed key and determining whether the card holder matches the key input from the external input device, the card can be authenticated or the authenticity of the card holder can be determined. .
[0019]
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a schematic configuration of an apparatus for manufacturing a card in which a digital watermark is embedded according to an embodiment of the present invention. As shown in FIG. 1, a card manufacturing apparatus 10 includes a card information database 20 including information necessary for issuing a card, a digital image generation unit 30 that embodies a digital image using the card information, and a user key value. The digital camera includes a watermark generation unit 40 for generating a watermark, a watermark embedding unit 50 for embedding the generated watermark in a digital image, and a digital image printing unit 60 for printing the digital image with the watermark embedded on a card.
[0020]
Next, with reference to FIG. 2, a description will be given of steps of manufacturing a card in which a watermark is embedded by the card manufacturing apparatus.
[0021]
The card information database 20 stores information and key values necessary for card issuance of a card issuance applicant, and data related to various types of card use. The key value and the information to be printed on the card are extracted (step S100). The data extracted in this way creates a basic digital image to be printed on the raw material of the card based on the information extracted from the card information database 20 using a card production graphic tool. In the graphic tool, after setting a predetermined area in consideration of the size of the card to be printed, various data are written in a preset position to create one data file (step S110).
[0022]
Further, the watermark generation unit 40 generates a watermark using the user key extracted from the card information database 20 (Step S120). The generated watermark is embedded in the digital image (step S130). The watermark generated by the watermark generation unit 40 is embedded in the digital image by the watermark embedding unit 50 (Step S130). Finally, the digital image with the watermark embedded therein is printed on the raw material of the card, thereby completing the production of the card with the watermark embedded therein (step S140). In particular, in the present invention, a method different from the conventional one is newly applied in order to generate and embed a watermark to be embedded in a card, which will be described with reference to FIGS.
[0023]
FIG. 3 is a detailed block diagram specifically showing the watermark-related configuration in FIG. 1, and FIG. 4 is a flowchart showing steps for producing a digital image in which a watermark is embedded by the configuration in FIG.
[0024]
FIG. 3 shows a detailed configuration of the watermark generation unit 40 and the watermark embedding unit 50. The watermark generation unit 40 includes a user key encryptor for encrypting a user key input from the card information database 20. 41, and a pseudorandom number generator 42 for generating a pseudorandom number from an encrypted user key. In addition, the watermark embedding unit 50 performs a black-and-white / color image discriminator 100 for discriminating whether an input digital image is black and white or color, and performs image processing when the input image is color. A color model converter 110 for converting a color model for easy execution, a frequency domain converter 120 for converting an input signal from a spatial domain to a frequency domain, and a watermark generated by the watermark generating unit 40 in a frequency domain. A watermark embedding unit 130 for embedding in the converted digital image, an inverse frequency domain converter 140 for converting the watermarked digital image from the frequency domain to the spatial domain, In some cases, an inverse color model converter 150 is provided for converting to the original color model.
[0025]
Next, with reference to FIG. 4, the operation of the watermark generation unit 40 and the watermark embedding unit 50 having such a configuration will be described.
[0026]
The digital image generated by the digital image generation unit 30 is input to the watermark embedding unit 50 (Step S200). The input digital image is input to the black-and-white image / color image discriminator 100, and determines whether the digital image in which the watermark is to be embedded is a black-and-white image or a color image (step S210). The black-and-white image / color image discriminator 100 extracts image information data relating to the format of the input digital image, and judges whether the image data is a black-and-white image or a color image from the extracted image information data.
[0027]
As a result of the discrimination by the black-and-white image / color image discriminator 100, if the corresponding digital image is black and white, it is converted to the frequency domain by the frequency domain converter 120 (step S220) ₁ ). At this time, since the black-and-white image has only a luminance component, the frequency domain converter 120 immediately converts the spatial domain to the frequency domain.
[0028]
On the other hand, if the result of the discrimination by the black-and-white / color image discriminator 100 is a color image, first, in the color model converter 110, for example, HSB (H: hue, S: saturation, B: brightness) ) Mode, YIQ (Y: luminance, I: in-phase, Q: quadrature) mode or YCbCr (Y: luminance, Cb / Cr: chrominance) mode is converted to a color model. It is extracted (step S215). The luminance component of the color model converted by the color model converter 110 is converted to the frequency domain by the frequency domain converter 120 (step S220). ₂ ). Although there are various techniques for converting a digital image into the frequency domain, typically, an FFT transform (Fast Fourier Transform), a DCT transform (Discrete Cosine Transform), a DWT transform (Discrete Wavelet Transform) and the like are used.
[0029]
In the present invention, the frequency domain method is used for embedding and detecting the watermark. This is because the conversion by the frequency domain method converts the digital image into the frequency domain, thereby concealing the watermark in the digital image. This is because there is an advantage that it is difficult to remove the watermark and the quality of the original digital image is not significantly reduced. According to the frequency domain transformer 120, a DCT coefficient, FFT coefficient or DWT coefficient (FOI) of the digital image is obtained.
[0030]
However, in the Fourier transform, it is difficult to embed watermark information in the Fourier transform coefficients because the coefficients in the transform domain are complex numbers. On the other hand, the DCT transform has characteristics similar to those of the Fourier transform. It is more advantageous and easier than the Fourier transform because the coefficients of the region consist only of real numbers. Here, an embodiment will be described in which a watermark is embedded in a DCT transform coefficient or a DWT transform coefficient relating to a digital image. The DCT transform is basically closely related to the FFT transform, and is a transform technique widely used in standard JPEG compression and the like. The one-dimensional DCT transform is defined as in the following Equation 1.
[0031]
(Equation 1)

[0032]
In Equation 1, s is the original signal value, t is the converted signal value, N indicates the signal length, and coefficient c is defined as in Equation 2 below.
[0033]
(Equation 2)

[0034]
(However, 1 ≦ k ≦ N−1).
Further, the two-dimensional DCT transform for a square matrix is defined as in the following Expression 3.
[0035]
[Equation 3]

[0036]
In Equation 3, N, s, and t have the same meaning as in the one-dimensional DCT transform, and c (i, j) is defined as in Equation 4 below.
[0037]
(Equation 4)

[0038]
(However, it is the case of i ≠ 0, j ≠ 0).
The DCT transform has an inverse transform, and is defined as one of the following equations 5 and 6 for one dimension and two dimensions, respectively.
[0039]
(Equation 5)

[0040]
(Equation 6)

[0041]
Next, DWT conversion will be described. If the Fourier transform is a transform using a sine function and a cosine function as basis functions, the wavelet transform is a transform using a wavelet as a basis function, and is roughly classified into a continuous wavelet transform and a discrete wavelet transform. The continuous wavelet transform is represented by the following equation (7).
(Equation 7)

[0042]
In Equation 7, s denotes scaling, τ denotes position translation, and Ψ (s, t) denotes a scaled and position-shifted wavelet.
[0043]
Scaling is related to frequency; low scaling, ie, a compressed wavelet, extracts high frequency components, and high scaling, ie, an expanded wavelet, extracts low frequency components. In general, a continuous wavelet transform cannot be actually implemented because the wavelet coefficients obtained by the transform are obtained infinitely as a function of scaling and position movement.
[0044]
Therefore, when a discrete wavelet transform that selects only a certain frequency region for scaling and position movement is used, it can be more effectively realized. However, since the discrete wavelet transform also requires a great deal of computational load to be realized by a computer, it is preferable to convert an image using a filter bank, which is a fast wavelet transform. This method uses a classical two-channel sub-band coding and pyramid algorithm, and can be easily realized as long as a relationship between filter banks for inverse transform (PR-QMF: Perfection reconstruction quadrature mirror filter) is established. There is an advantage that you can do it.
[0045]
The watermark generation unit 40 receives a predetermined user key from the card information database 20 and generates a watermark from the user key. When a user key is used as a watermark, the correlation between the detected watermark and the watermark generated from the user key can be used to more accurately determine whether the digital image is true or false, and whether the digital image has been modified. It has the advantage of strengthening.
[0046]
Further, before generating a pseudo-random number used as a watermark from the user key, the user encrypts the user key using the encryptor 41 and then inputs the encrypted key, and the pseudo-random number generator 42 Generate pseudorandom numbers. When the user key goes through the encryption step, not only is the user key value not easily transformed, but also the user key itself can be concealed, so that when a watermark generated from the encrypted user key is embedded in a digital image, Another advantage is that the user key itself is not exposed when a watermark is detected from a digital image. For encryption, a normal encryption method, for example, a DES (data encryption standard) method, an RSA method, an ECC method, or the like can be used. In the present invention, a PN-code method is used in which data to be encrypted is coded and the result is output as a pseudo random number (pseudo random number).
[0047]
When the watermark is generated in this manner, the watermark is embedded in the digital image by the watermark embedding unit 130 through the process of the following mathematical formula 5 (step S230). ₁ Or S230 ₂ ).
[0048]
(Equation 8)

[0049]
Here, fx is a characteristic function for adjusting the strength of the watermark embedded in the digital image. fx can be variously set, and modulo a part of a frequency domain transform coefficient (FOI) of a digital image or calculate a statistical characteristic value such as an average, a standard deviation, and a variance of a large number of transform coefficients. It may be a function to retrieve.
[0050]
FOI ′ indicates a result obtained by applying a watermark (W) to a value obtained by applying a characteristic function fx to a frequency domain transform coefficient (FOI) of a digital image. Since the transform coefficient (FOI) in Equation 5 is a value in the frequency domain of the digital image, the transform coefficient (FOI) has a form of a two-dimensional array, and the watermark (W) has a form of a one-dimensional permutation (sequence). FOI) in the form of a permutation, or the watermark (W) is converted into a two-dimensional block for calculation. For the calculation, one watermark can be matched and calculated for each frequency coefficient of an image, and there is a method in which the statistical properties of the frequency coefficients of a plurality of images are obtained and one watermark is calculated.
[0051]
Next, the step of embedding the watermark will be described in detail with reference to Equation 8.
The watermark embedding unit 130 applies a watermark to a value obtained by applying a characteristic function fx to an absolute value of a transform coefficient (hereinafter referred to as an embedding coefficient) in a predetermined specific frequency region (FOI ′; (Replacement coefficient) is replaced with another predetermined specific frequency domain transform coefficient. For example, when a digital image is divided into a low frequency region, an intermediate frequency region, and a high frequency region, a watermark is embedded in an intermediate frequency region or a high frequency region in which information of the digital image is relatively small. Watermarking is performed by substituting the conversion coefficients of the existing intermediate frequency domain and high frequency domain with the result (substitution coefficient) obtained by applying a watermark to the value obtained by applying the characteristic function fx to the conversion coefficient (embedding coefficient) of the domain. Is completed.
[0052]
According to such a scheme, even if there is a deformation such as a compression step or blurring that discards a part of the high-frequency part, the watermark is multiplied by the coefficient in the low-frequency area and replaced by the high-frequency area. Since a considerable portion of the high-frequency region remains even after the deformation, there is an advantage that it is resistant to deformation.
[0053]
In this specification, an example is shown in which the watermark is multiplied by the result of applying the characteristic function fx to the absolute value of the coefficient in the low frequency region, and is substituted between the intermediate frequency region and the high frequency region. Alternatively, a watermark may be embedded by selecting a frequency region within a range that does not degrade the quality of the digital image. For example, after watermarking the result of applying the characteristic function to the absolute value of the transform coefficient in the high frequency domain, it is possible to substitute for the high frequency domain, so the method of embedding the watermark in the digital image converted to the frequency domain is The present invention is not limited to this, and can be applied to various frequency ranges.
[0054]
Also, the present invention focuses on the fact that the overall characteristics of an image are not significantly changed by printing, and compensates for coefficients in other frequency regions with coefficients in an arbitrary frequency region, thereby changing the overall characteristics of the image. If the characteristic of the frequency domain where the image is not given is used, the characteristic becomes strong in printing, so that it is possible to prevent the watermark from disappearing by printing or the like. In addition, according to the watermark embedding method using the characteristics of the frequency domain described above, even if the watermark is embedded, the overall characteristics of the digital image do not change, that is, since the quality of the original digital image does not decrease, even after printing. It is possible to appreciate the quality of the original digital image.
[0055]
In equation (8), when a watermark is embedded in a digital image, the function that adjusts the strength of the watermark is the fx function. This characteristic function value can be arbitrarily set by the user, so that any value is possible. In particular, the characteristic function value can be determined by an appropriate function so that the quality of the digital image is not deteriorated by embedding the watermark (W). . That is, since the strength of the watermark and the deformation of the quality of the digital image are in inverse proportion to each other, it is preferable to determine the strength in consideration of the environment in which the watermark is used and the aspect of maintaining the quality of the digital image.
[0056]
Next, in order to obtain a digital image in which the watermark is embedded, the inverse frequency domain transformer 140 restores the digital image transformed in the frequency domain (step S240). ₁ Or S240 ₂ ). When the frequency domain transformer 120 uses DCT, DWT, or FFT transform, the inverse frequency domain transformer 140 uses inverse DCT, inverse DWT, or inverse FFT. Here, when the digital image is a color image, the inverse color model converter 150 converts the luminance component subjected to the inverse frequency domain conversion and the remaining components excluding the luminance component not subjected to the frequency domain conversion. Then, the original color model is restored from the color model in the HSB mode, the YIQ mode or the YCbCr mode (step S245). Finally, the process of embedding the watermark in the digital image is completed by obtaining the digital image in which the watermark is embedded (step S250).
[0057]
In this way, when the step of embedding the watermark in the digital image is completed, the card in which the watermark is embedded can be manufactured by printing the raw material of the card from the digital image printing unit 60 on the surface of the card.
[0058]
In the thus manufactured card in which the watermark according to the present invention is embedded, the embedded watermark can be variously determined according to the position and the content. Whether the content of the watermark is a character, a number, or an image, or the position where the watermark is embedded in the whole or a part of the card is determined variously depending on the characteristics of the watermarking technique selected by the card producer / issuer. For example, in the above-described step of manufacturing a card in which a watermark is embedded, if the part in which the watermark is to be embedded is a photograph of the card issuer, first leave a predetermined space in which the photograph is printed as a blank space, and in addition to the photo, After printing only the information to be printed on the card's raw material, a photo of the card issuer is produced as a digital image, a watermark is embedded only in this digital image, and the digital image with the watermark is embedded in the card. It may be printed at a predetermined position on the raw material. On the other hand, if the part where the watermark is to be embedded is the entire card, the information to be printed on the card is produced in a digital image of the same size as the entire card material, and then the watermark is embedded in this digital image. , May be printed on the raw material of the card. Alternatively, when the watermark is embedded in a specific portion of the image printed on the card, a method of displaying a specific identifier on the portion where the watermark is embedded may be used.
[0059]
Hereinafter, an apparatus and a method for authenticating a card in which a watermark created through such a manufacturing step is embedded will be described with reference to FIGS. The steps and apparatus for authenticating a card with an embedded watermark are configured to correspond to the steps for making a card and the apparatus described above, and the watermark detection technique used in the step of authenticating a card with an embedded watermark includes: Corresponds to the watermark embedding technique used in the step of producing a watermarked card.
[0060]
FIG. 5 is a block diagram showing a configuration of a card authentication device for authenticating a card manufactured by the card manufacturing device in FIG. The card authentication device 200 in FIG. 5 is roughly divided into a part for generating a watermark by inputting a user key and a part for processing information recorded on the card itself. The information recorded on the card itself includes a watermark included in digital information printed on the surface of the card and card user information recorded using a magnetic line. The card authentication device 200 may be configured to be linked with a database so that the card authenticator can confirm not only the card authentication but also information such as personal identification information and the breakdown of the card. Does not include a separate card information database.
[0061]
The card authentication device 200 uses a card recognition unit 210 for recognizing information included in a card, a key input unit 220 for inputting a user key, and data extracted from the card recognition unit 210. A database search information extraction unit 230 that searches and extracts information on a card of the corresponding user, a card information database unit 240 that extracts desired information from a card certifier among the extracted information, and a card recognition unit 210 A digital image data processing unit 250 that performs processing steps such as extraction of a digital image of a recognized card, and performs authentication using a watermark generated based on the extracted digital image and a user key input from the key input unit 220 The apparatus includes a watermark authentication server 260 and a result output unit 300 that outputs an authentication result.
[0062]
Hereinafter, with reference to FIG. 6, the operation of each component in the card authentication device 200 having such a configuration and the overall operation steps will be described.
[0063]
The card authenticator inserts the card into the card recognition unit 210 of the authentication device for the card in which the watermark is embedded and checks the key value in order to confirm whether the card is falsified or falsified and the authenticity of the card holder. Is input from the key input unit 220 (step S300). The card recognition unit 210 transmits various card information read from the card inserted by the card holder, such as a card serial number and a card user ID, to the database search information extraction unit 230, and also converts an image printed on the card. The scanned image is transmitted to the digital image data processing unit 250 in the format of digital image data.
[0064]
The database search information extraction unit 230 is a search unit for the card certifier to extract desired information, such as the identity information of the card holder and the details of the transaction, from the various card information transmitted from the card recognition unit 210. The information (card serial number, user ID, etc.) is extracted and sent to the card information database unit 240. Extraction of search information is performed by a part recorded in an element that performs information recording and display functions, such as a magnetic line and a bar code attached to a card. The card information database unit 240 extracts information about a predetermined card user desired by the card authenticator using the search information from the database search information extraction unit 230, and transmits the extracted information to the result output unit 300. The step of obtaining card user information ends (steps S340 to S360).
[0065]
Also, the digital image data processing unit 250 captures only the image in the area corresponding to the digital image area in which the watermark is embedded and transmits the image to the watermark authentication server 260 when the card in which the watermark is embedded is manufactured. The size of the image in the area to be captured may be within the size of the card, and is not particularly limited. At this time, in order to detect the watermark from the image printed on the card surface, it is necessary to know the position where the watermark is embedded, so in the step of embedding the watermark, if the watermark embedding area is determined in advance, At the time of watermark detection, only an image at a position corresponding to the area needs to be obtained. Alternatively, when embedding a watermark and embedding a separate identifier for displaying the embedding area, after searching for the identifier, only the image in the area determined by the identifier is captured. For high-speed transmission to the watermark authentication server 260, the image data in which the watermark is embedded may be compressed.
[0066]
The watermark authentication server 260 detects a watermark from the captured image data (Step S310). For the detection of the watermark, a detection method corresponding to the watermark technique applied at the time of embedding is used. The detected watermark is compared with the watermark generated by the user key (step S320), the result of the authentication based on the comparison result is output in a predetermined format that can be confirmed by the card authenticator, and the steps of detecting and authenticating the watermark are completed (step S320). Step S330). The watermark authentication server 260 performing such a function includes a watermark detection unit 270 that performs conversion to a frequency domain and detects a watermark using a frequency domain coefficient, and encrypts a key input by a user and then encrypts the key. A watermark generation unit 290 that generates a watermark using a key; and a comparison operation unit 280 that determines the presence or absence of authentication based on the correlation between the watermark detected by the watermark detection unit 270 and the watermark generated by the watermark generation unit 290. I have.
[0067]
Hereinafter, a watermark detection method will be described with reference to FIGS.
The watermark detection unit 270 of the watermark authentication server 260 receives the watermark embedded image from the digital image data processing unit 250 and detects the watermark according to the detection method of the present invention. If the digital image data processing section 250 compresses the image data, the watermark detection section 270 detects the watermark after decompressing the image data correspondingly.
[0068]
Further, the card holder inputs a key value to the key input unit 220 of the card authentication device 200. The key input unit 220 transmits the key value input from the card holder to the watermark authentication server 260 as digitized data. The watermark generation unit 290 of the watermark authentication server 260 encrypts the key data transmitted from the key input unit 220 by the same method as that used when embedding the watermark, and generates a watermark using the encrypted key data.
[0069]
Next, the comparison operation unit 280 determines the presence or absence of authentication based on the correlation between the watermark detected by the watermark detection unit 270 and the watermark generated by the watermark generation unit 290, and transmits the authentication result to the result output unit 300. .
[0070]
Finally, the result output unit 300 outputs the predetermined information desired by the card authenticator extracted from the card information database unit 240 and the authentication result transmitted from the comparison operation unit 280 of the watermark authentication server 260 to the card authenticator. Output in a form that can be confirmed.
[0071]
In the above steps, when it is confirmed from the card recognition unit 210 whether or not the card has been inserted, a watermark detection and authentication step for authenticating the card and discriminating the authenticity of the card holder (steps S310 to S330). Steps (Steps S340 to S360) for searching and extracting card user information required by the card authenticator from the database are performed. Since the two steps are independent processes, it is preferable to perform the two steps in parallel because the processing time can be reduced.
[0072]
Hereinafter, the steps of detecting and authenticating a watermark in relation to the watermark embedding method used in the card manufacturing apparatus according to the present invention will be described in detail with reference to FIGS.
[0073]
FIG. 7 is a detailed block diagram specifically showing a configuration of the watermark authentication server in FIG. 5, and FIG. 8 is a flowchart showing a step of comparing a watermark of a card by the configuration in FIG.
[0074]
Since the blocks constituting the watermark authentication server in FIG. 7 are the same as the components in the watermark embedding unit described above, the description of the respective functions is omitted, and the overall operation is described.
[0075]
The digital image embedded with the watermark processed by the digital image data processing unit 250 is input to the monochrome / color image discriminator 410 (step S400). The monochrome / color image discriminator 410 determines whether the digital image in which the watermark is embedded is a monochrome image or a color image (step S410). If the digital image in which the watermark is embedded is a monochrome image, the frequency domain converter 430 performs frequency domain conversion on the luminance component (step S420). If the digital image is a color image, the color model converter 420 first executes the HSB mode. , YIQ mode or YCbCr mode (step S430). The frequency domain converter 430 performs frequency domain conversion of DCT, DWT, and FFT on the luminance component.
[0076]
In this way, the watermark embedded in the digital image is detected from the transform coefficients obtained after the frequency domain conversion for the digital image in which the watermark is embedded, and the original watermark is restored (step S450). The detection of a watermark is to perform a reverse process of a process of applying a watermark to a result obtained by applying a characteristic function to a coefficient in a predetermined specific frequency region and embedding the result in a coefficient in another predetermined specific frequency region. From the obtained digital image, a substitution coefficient (FOI ′) embedded in the above-described specific frequency region and an embedding coefficient (FOI) used for calculating the substitution coefficient (FOI ′) are obtained. Restore the watermark using the coefficients and the substitution coefficients.
[0077]
In addition, the watermark generating unit 290 receives the user key, encrypts the user key with the user key encryptor 440 in the same manner as the watermark embedding step, and generates the PN-code watermark (W) with the pseudo-random number generator 450. Will be. In addition to the method of generating a watermark from a user key, the generation of a watermark may include, for example, embedding and detecting any one of several watermarks previously stored in a predetermined storage medium. When the user key is not input in this manner, the watermark obtained from the embedding coefficient and the substitution coefficient is compared with, for example, some watermarks stored in advance to determine whether the predetermined watermark is embedded. Can be determined.
In this way, by analyzing the correlation between the restored watermark (WE) and the watermark (W) generated by the method used at the time of embedding the watermark, whether the digital image has a predetermined watermark is determined. No can be detected (step S460). However, if the watermark is a permutation having an arbitrary size value, the values of the embedding coefficient and substitution coefficient must be used to restore the watermark. For example, the watermark has only 1 and -1. In the case of a binary sequence, the watermark value can be restored only with the sign of the substitution coefficient, assuming that the value of the characteristic function fx is always a positive number.
[0078]
The correlation analysis performed by the comparison operation unit 280 determines the correlation between the detected watermark (WE) and the watermark (W) generated using the key input by the user, and the correlation value thereof. By confirming that the specified watermark is embedded, it is possible to determine whether the digital image inspected by the watermark authentication device 200 is true or false and whether there is any change.
[0079]
Hereinafter, a correlation between the watermarks (WE and W) and a method of obtaining the correlation value will be described. The correlation between the watermarks (WE and W) is obtained by the following equation (9).
[0080]
(Equation 9)

[0081]
here,
[0082]
(Equation 10)

[0083]
Indicates a conjugate complex number of FFT (W), and IFFT (W) indicates an inverse FFT (W). The result of the correlation obtained from Equation 9 is not a single value, but a sequence form X ₁ ... X _N Therefore, a plurality of obtained values X ₁ ~ X _N To find the maximum peak value M and its position P. Thereafter, the kurtosis, that is, the fourth moment (Kurtosis) K, is obtained from the following Expression 11 from the result of the correlation obtained from Expression 9.
[0084]
(Equation 11)

[0085]
Where X ₁ ... X _N Is a sequence obtained from Expression 9 as described above, and is a result value of a correlation between watermarks (W and WE).
[0086]
(Equation 12)

[0087]
Is X ₁ ... X _N And σ represents the standard deviation.
[0088]
By analyzing the correlation values K, M, and P obtained in this way, it is possible to determine whether the watermark (W) generated with a predetermined user key matches the detected watermark (WE). More specifically, if the correlation value K, that is, the kurtosis (Kurtosis) is less than a predetermined threshold value, it indicates that the watermarks (W and WE) do not match, and the maximum peak value M is less than the predetermined threshold value. This also indicates that the watermarks (W and WE) do not match. Also, it means that the watermark (W and WE) matches only when the position P of the maximum peak value of the watermark (W and WE) is always the same.
[0089]
In addition, since the pseudo random number generated by the watermark generation unit has a correlation of '0' with pseudo random numbers other than its own signal, if the correlation of the pseudo random number is also equal to or greater than a predetermined threshold, This means that the watermarks (W and WE) match. Therefore, if the digital image satisfies all of the above-described correlation value conditions, it means that the watermarks (W and WE) match, so that the authentication of the digital image can be determined.
[0090]
Industrial applicability
As described above, according to the present invention, it is possible to prevent illegal acts that can be added to cards such as credit cards, IC cards, smart cards, student ID cards, employee ID cards, and card keys, and to falsify such cards. Can be easily detected, and an authentication effect of confirming / determining the authenticity of the card and the card holder can be obtained. In particular, if linked with a database system, identity information can be simultaneously grasped in addition to authenticity authentication of a card. In addition, it is not affected by contact with the magnetic material and the like, and the handleability is good.
[0091]
As described above, the preferred embodiments of the method of manufacturing a card with an embedded watermark according to the present invention, the authentication method, and those devices have been disclosed and described by way of example. However, it is apparent that such an embodiment is merely an example, and the present invention is not limited to this, and various changes, modifications, and substitutions can be made within the scope of the technical idea of the present invention. It is.
Further, the technical idea of the present invention is not limited to the above-described embodiment, but is limited only by the appended claims and technical principles equivalent thereto.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an apparatus for manufacturing a card in which a digital watermark is embedded according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating steps of manufacturing a card in which a watermark is embedded by the card manufacturing apparatus in FIG. 1;
FIG. 3 is a detailed block diagram specifically showing a watermark-related configuration in FIG. 1;
FIG. 4 is a flowchart showing steps of producing a digital image in which a watermark is embedded by the configuration shown in FIG. 3;
FIG. 5 is a block diagram illustrating a configuration of a card authentication device for authenticating a card manufactured by the card manufacturing device in FIG. 1;
FIG. 6 is a flowchart showing a card authentication step in the card authentication device in FIG. 5;
FIG. 7 is a detailed block diagram specifically showing a configuration of a watermark authentication server in FIG. 5;
8 is a flowchart showing a step of comparing a watermark of a card with the configuration shown in FIG. 7;

Claims (19)

In a card manufacturing device in which information for authentication is embedded,
Means for storing card issuance information and card authentication information of the card issuance applicant;
Means for converting the card issuing information of the storage means into a digital image having a shape of a predetermined size,
Means for setting the card authentication information of the storage means with a user key, and generating a watermark using the user key;
Means for embedding the watermark in the digital image;
Means for printing the digital image in which the watermark is embedded on the raw material of the card. The watermark generation means,
Means for encrypting the user key;
2. The card manufacturing apparatus according to claim 1, further comprising: means for generating a watermark in the form of a pseudo-random number using the encrypted user key. The watermark embedding means,
Frequency domain conversion means for converting the luminance component of the digital image into frequency domain coefficients,
The first frequency domain coefficient and the replacement coefficient generated using the watermark among the frequency domain coefficients are replaced with the second frequency domain coefficient among the frequency domain coefficients. Watermark embedding means for embedding a watermark,
3. The card manufacturing apparatus according to claim 2, further comprising: an inverse frequency domain conversion unit that performs an inverse frequency domain conversion of the digital image converted into the frequency domain and having a watermark embedded therein. A black-and-white / color image determining unit that determines whether the digital image is a black-and-white image or a color image;
When the digital image is a color image,
Color model conversion means for converting the digital image into a color model including a luminance component, extracting the luminance component of the converted color model, and sending the extracted luminance component to the frequency domain conversion means,
The digital image converted by the inverse frequency domain conversion means, using the luminance component subjected to the inverse frequency domain conversion and the remaining components excluding the luminance component not subjected to the frequency domain conversion, a color model 4. The card manufacturing apparatus according to claim 3, further comprising a color model reverse conversion unit for performing a reverse conversion. The card manufacturing apparatus according to claim 4, wherein the position of the watermark embedded in the digital image by the watermark embedding unit is set in advance. 5. The card manufacturing apparatus according to claim 4, wherein a watermark to be embedded in the digital image by the watermark embedding unit is embedded together with a specific identifier designating an embedding position. In the method of manufacturing a card in which information for authentication is embedded,
Converting the card issuing information from the card issuing information and the card authentication information relating to the card issuing applicant into a digital image having a shape of a predetermined size;
Setting the card authentication information of the storage means with a user key, and generating a watermark using the user key;
Embedding the watermark in the digital image;
Printing the digital image in which the watermark is embedded on the material of the card. The watermark generating step includes:
Encrypting the user key;
Generating a watermark in the form of a pseudo-random number using the user key. The watermark embedding step includes:
Converting a luminance component of the digital image into a frequency domain coefficient;
The first frequency domain coefficient and the replacement coefficient generated using the watermark among the frequency domain coefficients are replaced with the second frequency domain coefficient among the frequency domain coefficients. Embedding a watermark;
9. The method according to claim 8, further comprising the step of: inversely frequency domain transforming the digital image converted to the frequency domain and having the watermark embedded therein. The digital image is a color image,
Converting the digital image into a color model including a luminance component, and extracting the luminance component of the converted color model, before the method converts the luminance component into a frequency domain coefficient of the luminance component;
After the inverse frequency transforming step of the digital image, using the remaining components excluding the luminance component and the luminance component that has not been subjected to the frequency domain transform, and performing a color model inverse transform. The method for producing a card according to claim 9. The method according to claim 9, wherein the first frequency region is a low frequency region, and the second frequency region is a high frequency region. An authentication device for a card manufactured by the card manufacturing method according to claim 9,
Means for scanning the image printed on the card to generate a digital image;
Means for the card holder to input card authentication information;
A watermark generated using the card authentication information input from the card holder,
Means for calculating a correlation between the digital image and the watermark detected from the digital image to determine the presence or absence of authentication. The authentication determining means,
Means for generating a watermark using the card authentication information input from the card holder,
Watermark detection means for detecting and restoring a watermark embedded in the digital image,
13. The card authentication device according to claim 12, further comprising: means for calculating a correlation between the generated watermark and the restored watermark to determine whether the card has been authenticated. The watermark generation means,
Means for setting a user key and encrypting the card authentication information,
14. The card authentication apparatus according to claim 13, further comprising: means for generating a watermark in the form of a pseudo-random number using the encrypted user key. The watermark detection means,
Means for converting the luminance component of the digital image in which the watermark is embedded into frequency domain coefficients,
Means for detecting a watermark embedded in the digital image using the coefficients in the first frequency domain and the coefficients in the second frequency domain;
14. The card authentication device according to claim 13, further comprising: means for authenticating the digital image by obtaining a correlation between the detected watermark and the authentication watermark. A database in which information on the card user is stored,
Means for extracting database search information from the card;
The card authentication apparatus according to claim 14, further comprising: means for searching the database using the database search information, and outputting information on the card user. The scanned image includes an identifier indicating a position where a watermark is embedded, and the digital image generating unit searches for the identifier and obtains only digital image data in an area defined by the identifier. The card authentication device according to claim 12, which performs the authentication. After embedding a watermark generated using the card authentication information into digital image data converted from the card issuance information, producing the watermarked digital image data on a card material by an apparatus or method. In the authentication method of the issued card,
Scanning the image printed on the card to generate digital image data;
Obtaining digital image data of an area in which a watermark is embedded from the digital image data;
Detecting a watermark from the digital image data in the region in which the watermark is embedded;
A step of inputting card authentication information from a card holder;
Generating a watermark using the card authentication information input from the card holder,
Determining authentication from a correlation between the detected watermark and the generated watermark, and outputting the determined result. After embedding a watermark generated using the card authentication information into digital image data converted from the card issuance information, producing the watermarked digital image data on a card material by an apparatus or method. In the authentication method of the issued card,
Scanning the image printed on the card to generate digital image data;
Obtaining digital image data of an area in which a watermark is embedded from the digital image data;
Detecting a watermark from digital image data in the area where the watermark is embedded, and extracting card authentication information from the detected watermark;
A step of inputting card authentication information from a card holder;
Determining authentication based on a correlation between the extracted card authentication information and the input card authentication information, and outputting the determined result.

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