There are two types of digital signature mechanism:
- When the verification process needs the message as part of the input, the mechanism is called "signature mechanism with appendix". A hash-function is in used in the calculation of the appendix.
- When the verification process reveals all or part of the message, the mechanism is called a "signature mechanism giving message recovery". A hash-function is also used in the generation and verification of these signatures.
ISO/IEC 14888 specifies digital signatures with appendix. ISO/IEC 14888-1:2008 specifies general principles and requirements for digital signatures with appendix. ISO/IEC 14888-2 addresses digital signatures based on integer factoring, and ISO/IEC 14888-3 addresses digital signatures based on discrete logarithm.
Signature mechanisms giving message recovery are specified in ISO/IEC 9796. Hash-functions are specified in ISO/IEC 10118.