Final answer:
A digital signature is computed by hashing the message and encrypting the hash with the sender's private key. To verify it, the recipient decrypts the signature with the sender's public key and checks if the hash matches the one computed from the received message.
Step-by-step explanation:
When computing a digital signature, the process involves using a public key cryptographic system and a hash function. The message M is first passed through a hash function to produce a condensed and unique representation of the message, often denoted as h(M). This hash value is then encrypted with the sender's (Alice's) private key to create the signature S, expressed as S = [h(M)]Alice(1), where Alice(1) signifies the use of Alice's private key in the encryption process. This entire process is known as signing the message.
To verify a digital signature, the receiver will use Alice's public key to decrypt the signature S and retrieve the hash value that was originally created by Alice. The receiver then computes the hash of the received message using the same hash function to ensure that it matches the decrypted hash value. If the values match, the signature is considered valid, proving that the message was indeed sent by Alice and has not been tampered with during transit.A digital signature is computed using a combination of a public key system and a hash function. First, the message M is hashed using a hash function to produce the hash value h(M). Then, the hash value is encrypted using Alice's private key to generate the signature S. The signature S is a mathematical representation of the message that can be used to verify its authenticity.To verify a digital signature, the recipient uses Alice's public key to decrypt the signature S and obtain the hash value h(M). The recipient then independently calculates the hash of the received message M using the same hash function. If the calculated hash value matches the decrypted hash value, the signature is considered valid and the message is deemed authentic.