ISO/IEC 14888 specifies several digital signature mechanisms with appendix for messages of arbitrary length.This part of ISO/IEC 14888 contains general principles and requirements for digital signatures with appendix.It also contains definitions and symbols which are used in all parts of ISO/IEC 14888.Various means are available to obtain a reliable copy of the public verification key, e.g., a public keycertificate. Techniques for managing keys and certificates are outside the scope of ISO/IEC 14888. For further information, see ISO/IEC 9594-8 [4], ISO/IEC 11770-3 [3] and ISO/IEC 15945 [5].