A padding scheme is merely a standard method of ensuring that the input
to be encrypted is a multiple of the cipher's block size. The padding
schemes of GNU Crypto are in package `gnu.crypto.pad`

and include:

**PKCS #7**. PKCS #7 (referred to as "PKCS7" in GNU Crypto) pads the input P with the quantity w = b - (|P| \bmod b), where b is the cipher's block size, encoded as w bytes. That is, if the input is 5 bytes shorter than the required length, then the input is padded with the byte equal to 5 five times. This padding scheme supports block sizes of 2 \leq b \leq 256 bytes.**Trailing bit complement**. The "TBC" pad appends the complement of the last bit in the input until the input is the desired length. That is, if the last bit is`1`

, then the input is padded with`0`

, and if the last bit is`0`

, then the input is padded with`1`

. This padding scheme supports block sizes up to 256 bytes.