👉 In the context of cryptography, a "postsigner" is an entity that signs data in response to a cryptographic signature. In other words, it is a party that provides a proof of identity and signature for the original signer before signing the data. For example, in a digital signature scheme like RSA or ECC, the key used to sign a message is generated by the public key of the recipient, which is then verified against the private key of the signer. If the verification fails, the signer
