Public verifiability: anyone can verify the validity of the signature. B. unforgeability: it is difficult for others to forge their signatures except the legal signer. C. Uniqueness: the signature corresponds to the signed message one by one. All of the above are true.

Digital signature (also known as public key digital signature) is a digital string that can only be generated by the sender of information, and others cannot forge it. This number string is also an effective proof of the authenticity of the information sent by the information sender. It is a method to authenticate digital information, which is similar to the ordinary physical signature written on paper, but it is realized by using the technology in the field of public key encryption. A set of digital signatures usually defines two complementary operations, one for signing and the other for verification. Digital signature is the application of asymmetric key encryption technology and digital digest technology.