This International Standard describes four modes of operation for an n-bit block cipher algorithm.
NOTE 1 Annex A (informative) contains comments on the properties of each mode.
This International Standard establishes four defined modes of operation so that in applications of an n-bit block cipher algorithm (e.g. protection of data transmission, data storage, authentication) this International Standard will provide a useful reference for, for example, the specification of the mode of operation and the values of parameters (as appropriate).
For some modes, padding may be required to ensure that all plaintext variables are of the necessary length. Padding techniques a re not within the scope of this International Standard.
NOTE 2 For the Cipher Feedback (CFB) Mode of operation (see clause 6), two parameters j and k are defined. For the Output Feedback (OFB) Mode of operation (see clause 7), one parameter j is defined. When one of these modes of operation is used the parameter value(s) need(s) to be chosen and used by all communicating parties.