Electronic signature
lastmod 2019-01-17created 2019-01-173 edits
An electronic signature is information in electronic form that is attached to or logically combined with a specific electronic document, used to identify the signer and to indicate that the signer signed that electronic document.
- From the technical standpoint of public key infrastructure (PKI), an electronic signature is the hash (HASH) value of an electronic document transformed (encrypted) with the signer's private key (electronic signature creation data); the PKCS#7 standard created by RSA is widely used.
In other words, if the original document content is A, you pick a function such as SHA1, a well-known Hash function, use that Hash function to compute the Hash value of document A, and encrypt this Hash value with the Private Key of the sender (Cheolsu). Then the encrypted Hash value is attached to the end of the original document A, and the whole document is sent to the recipient (Yeonghui).
When the message arrives, Yeonghui first computes the Hash value of the received document, using the Hash function Cheolsu used, over the leading part of the document excluding the hash value. Next, she decrypts the encrypted Hash value attached to the end of the document with Cheolsu's decryption key, and compares this decrypted Hash value with the Hash value of the received document. If the two Hash values are identical, the signature is valid; if the values differ or the transformation fails, the signature is invalid.
- An electronic signature has the same legal effect as a handwritten signature.
A digital signature is the procedure by which the sender proves their identity, and an electronic signature is the information used at a specific step of that procedure.