Digital signature

Many public key methods are applicable to creation of digital signatures. For a digital signature, the signer computes a hash value from the message by means of a one-way function and encrypts the hash value with his private key. The recipient also computes a hash value from the message received and compares it to the encrypted hash value, which he has opened with the public key obtained from the signer’s certificate. If the hash values are equal, the message has not been modified during delivery and it has been signed by the person mentioned in the certificate.