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A digital signature is a public key cryptography application signature verification function. The aim is to ensure the integrity of information transmission, the sender's identity authentication, to prevent the occurrence of transaction repudiation. Which is an encrypted digital signature process, digital signature verification is a decryption process. The principle we must first understand the asymmetric encryption and message digest.
With asymmetric encryption public key is published, if the decryption with the public key can only open extract the contents of the corresponding private key encryption, so that the private key can also be considered as proof of personal identity. If the communication parties need to send messages, two mechanisms need to be established (i.e., two pairs of the public private key pair) non-symmetric encryption, one message is encrypted using the public key of the other party receiving the message using its private key decryption.
Message digest may be converted into a fixed message identifier unique hash value of the string length. Mean value uniquely different message digest are different conversion, and to ensure uniqueness. The process is irreversible, i.e., reverse thrust can not digest plaintext. Using this feature, you can verify the integrity of the message.
Is a combination of digital signature and message digest asymmetric encryption, the procedure is as follows:
Suppose there are two communication parties A and B, used between two sets of asymmetric encryption mechanisms.
A message now to B.
Then, if the transmission process, which was modified ciphertext message, B to get the ciphertext decryption after obtaining the plaintext, A is not transmitted, the information is incorrect. It is necessary to solve the following two questions:
Authentication of A
A sends the message integrity then they would use the basics of the above stated.
In order to solve two problems above, the digital signature process as shown below:
Simple explanation:
A: A summary of the operation to obtain a plain text summary (message integrity), then digest encrypted private key (authentication) by A to obtain the digital signature, the digital signature and a ciphertext sent B.
B: A message is received, the first ciphertext with his private decryption plaintext. After decrypting the digital signature with a public key of A, the correct summary (A successful decryption instructions identity is authenticated). Then plaintext digest calculation, comparison summary description message has not been tampered consistent (message integrity).