電子病歷的完整性及可信任性一直是推動無紙化過程中的一個重要議題。電子簽章通常用來確保電子病歷的完整性及可信任性的一個重要方法；但是在實際的應用上卻出現二個問題:(1)電子簽章的持續有效性；(2)使用者(醫事人員)對電子簽章的信賴度。通常電子簽章是以儲存在智慧卡中的金鑰，以不對稱加解密演算法對明文進行簽署。在醫療領域中，這張智慧卡通常被稱為醫事人員憑證。在3種情況下，醫事人員憑證中的金鑰對需要被註銷:(1) 憑證遺失;(2) 憑證過期;(3)憑證不再被使用(例如人員退休)。當憑證被註銷後，用這憑證所簽署過的電子病歷都無法被驗證。
本研究提出二個非RSA演算法為基礎的視覺化之向前式安全群組憑證電子簽章演算法，使得電子簽章具有向前式安全的功能。該功能可以避免電子簽章因為更換憑證而失去可驗證性，並導入群組的概念使本演算法在實際利用上產生階層性，以減少金鑰的數量，及縮短搜尋金鑰的時間。視覺化使得電子簽章在電子病歷上的呈現方式不再只是一串的亂碼，取而代之的是內含電子簽章的傳統印章或簽名的影像，以協助使用者將一般習用印章或簽名的信賴性延伸到電子簽章。
本研究提出的演算法較現有類似演算法效能為佳，能抵擋各種已知可能的攻擊，並實做雛型系統。結果顯示，所提出之電子簽章演算法確實可以達到向前式安全，且所計算出之電子簽章值也可以順利的驗證，以確保電子簽章的可信賴性。另外在視覺化的處理上，實驗結果顯示峰值信號雜訊比(PSNR)為60~70db。這個值介於可接受範圍60~80dB間。

Integrity and trustworthiness are important to electronic medical records. Digital signature is a significant method to ensure the integrity and trustworthiness of electronic medical records. The key(s) used to generate/verifying a medical staff’s digital signatures is generally stored in a smart card, which is called a medical personnel certificate. There are three situations that would force a certificate to be revoked: certificate expiration, loss of the certificate, and retirement of the certificate holder. An important issue is that after a certificate is revoked, the digital documents signed by the revoked certificate are longer verifiable.
This research presents two new visualized forward secure digital signature algorithms, which are not based on RSA algorithm, for electronic medical records. A digital signature generated by applying either of the proposed algorithms, has the capability as forward secure, which means even a medical staff’s certificate is revoked, the medical records signed by the revoked private key still can be verified. The idea of group certificate helps to reduce the number of certificates and the time of searching certificates. Also, in order to extend the trust from a visualized traditional seal or a handwritten signature to a digital signature, an approach is proposed to embed the digital signature into a seal image or a handwritten signature image of the holder instead of a human unrecognizable form.
Performance comparisons with existing methods, and security analysis are performed and a prototype is implemented to demonstrate the feasibility of the proposed approach. The peak signal to noise ratio (PSNR) of the digital signature visualization process is 60~70db, which is very good in human eyes’ recognition level (60~80dB).

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