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Update to docs and test cases

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Legrandin 2015-12-23 23:19:37 +01:00
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36
lib/Crypto/Cipher/DES.py
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@ -24,12 +24,13 @@
DES `(Data Encryption Standard)`__ is a symmetric block cipher standardized
by NIST_ . It has a fixed data block size of 8 bytes.
Its keys are 64 bits long, even though 8 bits were used for integrity (now they
are ignored) and do not contribute to securty.
are ignored) and do not contribute to securty. The effective key length is
therefore 56 bits only.
DES is cryptographically secure, but its key length is too short by nowadays
standards and it could be brute forced with some effort.
DES should not be used for new designs. Use `AES`.
**Use DES, not AES. This module is provided only for legacy purposes.**
As an example, encryption can be done as follows:
@ -106,22 +107,25 @@ def new(key, mode, *args, **kwargs):
key : byte string
The secret key to use in the symmetric cipher.
It must be 8 byte long. The parity bits will be ignored.
:Keywords:
mode : a *MODE_** constant
The chaining mode to use for encryption or decryption.
IV : byte string
iv : byte string
(*Only* `MODE_CBC`, `MODE_CFB`, `MODE_OFB`, `MODE_OPENPGP`).
The initialization vector to use for encryption or decryption.
It is ignored for `MODE_ECB` and `MODE_CTR`.
For `MODE_OPENPGP`, IV must be `block_size` bytes long for encryption
and `block_size` +2 bytes for decryption (in the latter case, it is
For `MODE_OPENPGP`, IV must be 8 bytes long for encryption
and 10 bytes for decryption (in the latter case, it is
actually the *encrypted* IV which was prefixed to the ciphertext).
It is mandatory.
For all other modes, it must be 8 bytes long.
If not provided, a random byte string is generated (you can read it
back via the ``iv`` attribute).
nonce : byte string
(*Only* `MODE_EAX` and `MODE_CTR`).
A mandatory value that must never be reused for any other encryption.
@ -130,15 +134,19 @@ def new(key, mode, *args, **kwargs):
For `MODE_EAX`, there are no restrictions, but it is recommended to
use at least 16 bytes.
counter : object
(*Only* `MODE_CTR`). An object created by `Crypto.Util.Counter`.
If not provided for `MODE_EAX`, a random byte string is generated (you
can read it back via the ``nonce`` attribute).
mac_len : integer
(*Only* `MODE_EAX`). Length of the MAC, in bytes.
(*Only* `MODE_EAX`). Length of the authentication tag, in bytes.
It must be no larger than 8 (which is the default).
segment_size : integer
(*Only* `MODE_CFB`).The number of bits the plaintext and ciphertext
are segmented in.
It must be a multiple of 8. If not specified, it will be assumed to be 8.
(*Only* `MODE_CFB`).The number of **bits** the plaintext and ciphertext
are segmented in. It must be a multiple of 8.
If not specified, it will be assumed to be 8.
initial_value : integer
(*Only* `MODE_CTR`). The initial value for the counter within
the counter block. By default it is 0.