加密填补 填充 pad padding

RFC 1423 - Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers https://tools.ietf.org/html/rfc1423

The input to the DES CBC encryption process shall be padded to a
   multiple of 8 octets, in the following manner.  Let n be the length
   in octets of the input.  Pad the input by appending 8-(n mod 8)
   octets to the end of the message, each having the value 8-(n mod 8),
   the number of octets being added.  In hexadecimal, the possible
   paddings are:  01, 0202, 030303, 04040404, 0505050505, 060606060606,
   07070707070707, and 0808080808080808.  All input is padded with 1 to
   8 octets to produce a multiple of 8 octets in length.  The padding
   can be removed unambiguously after decryption.

As described in PKCS #1, all quantities input as data values to the RSAEncryption process shall be properly justified and padded to the length of the modulus prior to the encryption process. In general, an RSAEncryption input value is formed by concatenating a leading NULL octet, a block type BT, a padding string PS, a NULL octet, and the data quantity D, that is, RSA input value = 0x00 || BT || PS || 0x00 || D.

   The input to the DES CBC encryption process shall be padded to a
   multiple of 8 octets, in the following manner.  Let n be the length
   in octets of the input.  Pad the input by appending 8-(n mod 8)
   octets to the end of the message, each having the value 8-(n mod 8),
   the number of octets being added.  In hexadecimal, the possible
   paddings are:  01, 0202, 030303, 04040404, 0505050505, 060606060606,
   07070707070707, and 0808080808080808.  All input is padded with 1 to
   8 octets to produce a multiple of 8 octets in length.  The padding
   can be removed unambiguously after decryption.