digital signature (e-signature)
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- How to read in Japanese: digital signature (e-signature)
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Digital signature is a technology that uses public key cryptography and hash functions to prove that a digital document was “definitely created by the sender” and “that it has not been altered”. It can be said to be an alternative to the signature and seal used for analog documents.
There are several types of e-signatures, including RSA, DSA, and ECDSA, with ECDSA being used for Bitcoin. ECDSA (Elliptic Curve DSA) is an improved version of DSA and is an elliptic curve DSA signature method.
DSA, on the other hand, is known for its adoption as the standard cipher of the U.S. National Institute of Standards and Technology (NIST). In addition, one of the earliest digital signature techniques proposed was RSA.
In digital signatures, the sender of a digital document first generates a “private key” and a “public key” and passes the “public key” to the recipient. Next, a hash value is calculated from the created document, encrypted with the “private key,” and sent together with the document to the recipient.
The recipient independently calculates the hash value from the received document. The hash value is then obtained by decrypting the encrypted document with the “public key”. If these two hash values match, it can be verified that the document was definitely created by the sender.
If the “public key” used here does not belong to the sender, the digital document itself loses credibility. Therefore, a third-party organization is needed to prove that the public key definitely belongs to the sender. This is a Certificate Authorities.
In Japan, the ESIGN Act of 2000 created regulations governing certification authorities. By attaching an electronic certificate issued by certification authority to the digital signature sent to the recipient, it is possible to increase the reliability of digital documents.