Editing Padding (cryptography) (section)

=====ISO/IEC 7816-4=====

[[ISO/IEC 7816]]-4:2005<ref>[http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=36134 ISO catalog, ''ISO/IEC 7816-4:2005'']</ref> is identical to the bit padding scheme, applied to a plain text of ''N'' bytes. This means in practice that the first byte is a mandatory byte valued '80' (Hexadecimal) followed, if needed, by 0 to ''N''&nbsp;−&nbsp;1 bytes set to '00', until the end of the block is reached. ISO/IEC 7816-4 itself is a communication standard for smart cards containing a file system, and in itself does not contain any cryptographic specifications.

Example:
In the following example the block size is 8 bytes and padding is required for 4 bytes

 ... | DD DD DD DD DD DD DD DD | DD DD DD DD '''80 00 00 00''' |

The next example shows a padding of just one byte

 ... | DD DD DD DD DD DD DD DD | DD DD DD DD DD DD DD '''80''' |