Eh xdZdZddlmZddlmZGddej ZdZdZd Z d Z d Z d Z d Z dZdZdZy)a(Triple DES symmetric cipher `Triple DES`__ (or TDES or TDEA or 3DES) is a symmetric block cipher standardized by NIST_. It has a fixed data block size of 8 bytes. Its keys are 128 (*Option 1*) or 192 bits (*Option 2*) long. However, 1 out of 8 bits is used for redundancy and do not contribute to security. The effective key length is respectively 112 or 168 bits. TDES consists of the concatenation of 3 simple `DES` ciphers. The plaintext is first DES encrypted with *K1*, then decrypted with *K2*, and finally encrypted again with *K3*. The ciphertext is decrypted in the reverse manner. The 192 bit key is a bundle of three 64 bit independent subkeys: *K1*, *K2*, and *K3*. The 128 bit key is split into *K1* and *K2*, whereas *K1=K3*. It is important that all subkeys are different, otherwise TDES would degrade to single `DES`. TDES is cryptographically secure, even though it is neither as secure nor as fast as `AES`. As an example, encryption can be done as follows: >>> from Crypto.Cipher import DES >>> from Crypto import Random >>> from Crypto.Util import Counter >>> >>> key = b'-8B key-' >>> nonce = Random.new().read(DES.block_size/2) >>> ctr = Counter.new(DES.block_size*8/2, prefix=nonce) >>> cipher = DES.new(key, DES.MODE_CTR, counter=ctr) >>> plaintext = b'We are no longer the knights who say ni!' >>> msg = nonce + cipher.encrypt(plaintext) .. __: http://en.wikipedia.org/wiki/Triple_DES .. _NIST: http://csrc.nist.gov/publications/nistpubs/800-67/SP800-67.pdf :undocumented: __revision__, __package__ z$Id$) blockalgo)_DES3ceZdZdZdZy) DES3CipherzTDES cipher objectcVtjj|t|g|i|y)zVInitialize a TDES cipher object See also `new()` at the module level.N)r BlockAlgo__init__r)selfkeyargskwargss S/var/www/html/bid_assistant/venv/lib/python3.12/site-packages/Crypto/Cipher/DES3.pyr zDES3Cipher.__init__Hs& $$T5#GGGN)__name__ __module__ __qualname____doc__r rrrrEs Hrrc t|g|i|S)aCreate a new TDES cipher :Parameters: key : byte string The secret key to use in the symmetric cipher. It must be 16 or 24 bytes long. The parity bits will be ignored. :Keywords: mode : a *MODE_** constant The chaining mode to use for encryption or decryption. Default is `MODE_ECB`. IV : byte string The initialization vector to use for encryption or decryption. It is ignored for `MODE_ECB` and `MODE_CTR`. For `MODE_OPENPGP`, IV must be `block_size` bytes long for encryption and `block_size` +2 bytes for decryption (in the latter case, it is actually the *encrypted* IV which was prefixed to the ciphertext). It is mandatory. For all other modes, it must be `block_size` bytes longs. It is optional and when not present it will be given a default value of all zeroes. counter : callable (*Only* `MODE_CTR`). A stateful function that returns the next *counter block*, which is a byte string of `block_size` bytes. For better performance, use `Crypto.Util.Counter`. segment_size : integer (*Only* `MODE_CFB`).The number of bits the plaintext and ciphertext are segmented in. It must be a multiple of 8. If 0 or not specified, it will be assumed to be 8. :Attention: it is important that all 8 byte subkeys are different, otherwise TDES would degrade to single `DES`. :Return: an `DES3Cipher` object )r)r r r s rnewrNsH c +D +F ++r)N)r __revision__ Crypto.CipherrrrrrMODE_ECBMODE_CBCMODE_CFBMODE_PGPMODE_OFBMODE_CTR MODE_OPENPGP block_sizekey_sizerrrr,sa,(T #H$$H$,N        r