Blowcurve Encryption Library

Repository: https://www.github.com/origamizyt/blowcurve

Simple library for Blowfish / ECC encryption and digital signatures.

Installation

This library is available on PyPI.

pip install blowcurve

Or you could also install from source code.

python setup.py install

Usage

The Blowcurve class in package root provides all usage. You can initialize it without any parameters to generate random keys: (In fact, this is the only way to create instances.)

>>> from blowcurve import Blowcurve
>>> bc1 = Blowcurve()
>>> bc2 = Blowcurve()

The export method allows you to export the key as DER hex string:

>>> bc1.export()
'3059301306072a8648ce3d020106082a8648ce3d030107034200041c873634bf4b14d555800e33482971ca55e5780e8c109c817adf185919060e414857851ee2bdff18cd76510b80c79f3b11380810e2be9a876765722ed9c7f465'

The load method performs ecdh key exchange with remote services:

>>> bc1.load(bc2.export())
>>> bc2.load(bc1.export())

No error means key exchange was successful.

After key exchange, the sign and encrypt methods are enabled:

>>> signature = bc1.sign(b'data')
>>> bc2.verify(b'data', signature)
True
>>> data = b'mymessage'
>>> bc2.decrypt(bc1.encrypt(data))
b'message'

If no remote key was provided, a MissingRemoteKey exception will be raised:

>>> Blowcurve().encrypt(b'')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "__init__.py", line 41, in encrypt
    ephemeral, key = self._pair.ephemeral()
  File "keys.py", line 94, in ephemeral
    raise MissingRemoteKey
blowcurve.keys.MissingRemoteKey: remote key not loaded yet.
>>> Blowcurve().verify(b'', b'')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "__init__.py", line 38, in verify
    return self._pair.verify(data, signature)
  File "keys.py", line 109, in verify
    raise MissingRemoteKey
blowcurve.keys.MissingRemoteKey: remote key not loaded yet.

The keys module has API for basic signing and ecdh.

>>> from blowcurve.keys import ECKeys
>>> k1 = ECKeys()
>>> k2 = ECKeys()
>>> k1.load(k2.export())
>>> k2.load(k1.export())
>>> k1.secret() == k2.secret()
True
>>> k2.verify(b'data', k1.sign(b'data'))
True

The crypt module has API for encryption and padding.

>>> from blowcurve import crypt
>>> crypt.pkcs5_pad(b'data', 8)
b'data\x04\x04\x04\x04'
>>> crypt.pkcs5_pad(b'mymessage', 16)
b'mymessage\x07\x07\x07\x07\x07\x07\x07'
>>> crypt.pkcs5_unpad(b'data\x04\x04\x04\x04')
b'data'
>>> crypt.pkcs5_unpad(b'incorrect\x01\x02\x03')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "crypt.py", line 41, in pkcs5_unpad
    raise IncorrectPadding
blowcurve.crypt.IncorrectPadding: incorrect padding
>>> data = crypt.encrypt(b'mykey', b'hello, world!')
>>> crypt.decrypt(b'mykey', data)
b'hello, world!'
>>> crypt.decrypt(b'other', data)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "crypt.py", line 71, in decrypt
    return pkcs5_unpad(cipher.decrypt(data))
  File "crypt.py", line 41, in pkcs5_unpad
    raise IncorrectPadding
blowcurve.crypt.IncorrectPadding: incorrect padding

The cause of the exception above is because the incorrect key results in incorrect decrypted data, therefore causing an incorrect padding. (There is chance that this exception won't occur, but the result will still be malformed.)

Testing

The test.py file contains unittest test cases:

$ python -m unittest --verbose blowcurve.test
testEncrypt (blowcurve.test.BlowcurveTestCase) ... ok
testSign (blowcurve.test.BlowcurveTestCase) ... ok
testEncrypt (blowcurve.test.CryptTestCase) ... ok
testPad (blowcurve.test.CryptTestCase) ... ok
testNoRemoteKey (blowcurve.test.KeysTestCase) ... ok
testSecret (blowcurve.test.KeysTestCase) ... ok
testSign (blowcurve.test.KeysTestCase) ... ok

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Ran 7 tests in 0.179s

OK