The expression AES.new(key) used to be equivalent
to AES.new(key, AES.MODE_ECB). The same applies to
any other algorithm beside AES.
Since the ECB mode is not a secure default,
the expression AES.new(key) will now raise an exception.
NOTE: this change sets breaks compatibility with PyCrypto
The main change done by this commit is adding support
for MODE_GCM (NIST SP 800 38D). Test vectors are included.
The mode uses a C extension (Crypto.Util.galois._ghash)
to compute the GHASH step. The C implementation is the most
basic one and it is still significantly (5x times) slower than CTR.
Optimizations can be introduced using tables (CPU/memory trade-off)
or even AES NI instructions on newer x86 CPUs.
This patch also simplifies Crypto.Cipher.blockalgo.py by:
* removing duplicated code previously shared by digest() and verify().
* removing duplicated code previously shared by Crypto.Hash.CMAC
and Crypto.Cipher.block_algo (management of internal buffers
for MACs that can only operate on block aligned data, like
CMAC, CBCMAC, and now also GHASH).
[dlitz@dlitz.net: Included changes from the following commits from the author's pull request:]
- [9c13f9c] Rename 'IV' parameter to 'nonce' for AEAD modes.
- [ca460a7] Made blockalgo.py more PEP-8 compliant;
The second parameter of the _GHASH constructor
is now the length of the block (block_size)
and not the full module.
[dlitz@dlitz.net: Replaced MacMismatchError with ValueError]
[dlitz@dlitz.net: Replaced ApiUsageError with TypeError]
[dlitz@dlitz.net: Replaced renamed variable `ht` with original `h`]
[dlitz@dlitz.net: Whitespace fixed with "git rebase --whitespace=fix"]
This patch add supports for SIV, an AEAD block cipher
mode defined in RFC5297. SIV is only valid for AES.
The PRF of SIV (S2V) is factored out in the Protocol.KDF module.
See the following example to get a feeling of the API (slightly
different than other AEAD mode, during decryption).
Encryption (Python 2):
>>> from Crypto.Cipher import AES
>>> key = b'0'*32
>>> siv = AES.new(key, AES.MODE_SIV)
>>> ct = siv.encrypt(b'Message')
>>> mac = siv.digest()
Decryption (Python 2):
>>> from Crypto.Cipher import AES, MacMismatchError
>>> key = b'0'*32
>>> siv = AES.new(key, AES.MODE_SIV)
>>> pt = siv.decrypt(ct + mac)
>>> try:
>>> siv.verify(mac)
>>> print "Plaintext", pt
>>> except MacMismatchError:
>>> print "Error"
This change also fixes the description/design of AEAD API.
With SIV (RFC5297), decryption can only start when the MAC is known.
The original AEAD API did not support that.
For SIV the MAC is now exceptionally passed together with the ciphertext
to the decrypt() method.
[dlitz@dlitz.net: Included changes from the following commits from the author's pull request:]
- [9c13f9c] Rename 'IV' parameter to 'nonce' for AEAD modes.
- [d7727fb] Fix description/design of AEAD API.
- [fb62fae] ApiUsageError becomes TypeError [whitespace]
- [4ec64d8] Removed last references to ApiUsageError [whitespace]
- [ee46922] Removed most 'import *' statements
- [ca460a7] Made blockalgo.py more PEP-8 compliant;
The second parameter of the _GHASH constructor
is now the length of the block (block_size)
and not the full module.
[dlitz@dlitz.net: A conflict that was not resolved in the previous
commit was originally resolved here. Moved the
resolution to the previous commit.]
[dlitz@dlitz.net: Replaced MacMismatchError with ValueError]
[dlitz@dlitz.net: Replaced ApiUsageError with TypeError]
[dlitz@dlitz.net: Whitespace fixed with "git rebase --whitespace=fix"]
[dlitz@dlitz.net: Included changes from the following commits from the author's pull request:]
- [9c13f9c] Rename 'IV' parameter to 'nonce' for AEAD modes.
- [ca460a7] Made blockalgo.py more PEP-8 compliant; The second parameter
of the _GHASH constructor is now the length of the block
(block_size) and not the full module.
[dlitz@dlitz.net: Fixed unresolved conflict in lib/Crypto/Cipher/blockalgo.py]
[dlitz@dlitz.net: Included changes from the following commits from the author's pull request:]
- [5306cf3] Added support for CCM mode (AES cipher only)
- [9abe301] Added CCM tests
- [f0c1395] Add MacMismatchError and ApiUsageError
- [fb62fae] ApiUsageError becomes TypeError
- [9c13f9c] Rename 'IV' parameter to 'nonce' for AEAD modes.
- [4ec64d8] Removed last references to ApiUsageError
- [80bfd35] Corrected AES-CCM examples
[dlitz@dlitz.net: Removed unrelated documentation change]
[dlitz@dlitz.net: Renamed 'targs' back to 'args']
[dlitz@dlitz.net: Whitespace fixed with "git rebase --whitespace=fix"]
A new module (blockalgo) has been added. It contains a class (BlockAlgo)
all ciphers derive from. The only purpose of such base class
is to centralize all general documentation applicable to all block
ciphers (e.g. modes) into a single file.
