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Update demo_dynamic.py

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added error strings (with function returning a string type) and a decryption to ChCha.
This commit is contained in:
Larry Bugbee 2017-08-10 16:40:28 -07:00 committed by GitHub
parent 87d876f6ac
commit 695c3b235d
1 changed files with 23 additions and 6 deletions
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29
demos/demo_dynamic.py
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@ -1,7 +1,7 @@
"""
demo_dynamic.py v2
demo_dynamic.py v2b
This program demonstrates Python's use of the dynamic
language support additions to LTC, namely access to LTC
@ -33,11 +33,12 @@
mathlib. For example, public key crypto requires
a mathlib; hashing and symmetric encryption do not.
This code was written for Python 2.7.
This code was written for Python 2.7 with the ctypes standard
library.
Larry Bugbee
March 2014 v1
August 2017 v2
August 2017 v2b
"""
@ -195,6 +196,13 @@ def _get_constant(name):
raise Exception('LTC.crypt_get_constant(%s) rc = %d' % (name, rc))
return constant.value
def _err2str(err):
# define return type
errstr = LTC.error_to_string
errstr.restype = c_char_p
# get and return err string
return errstr(err)
CRYPT_OK = _get_constant('CRYPT_OK')
class SHA256(object):
@ -213,15 +221,17 @@ class ChaCha(object):
self.state = c_buffer(_get_size('chacha_state'))
self.counter = c_int(1)
err = LTC.chacha_setup(byref(self.state), key, len(key), rounds)
if err != CRYPT_OK:
raise Exception('LTC.chacha_setup(), err = %d, "%s"' % (err, _err2str(err)))
def set_iv32(self, iv):
err = LTC.chacha_ivctr32(byref(self.state), iv, len(iv), byref(self.counter))
if err != CRYPT_OK:
raise Exception('LTC.chacha_ivctr32() err = %d' % err)
raise Exception('LTC.chacha_ivctr32(), err = %d, "%s"' % (err, _err2str(err)))
def crypt(self, datain):
dataout = c_buffer(len(datain))
err = LTC.chacha_crypt(byref(self.state), datain, len(datain), byref(dataout))
if err != CRYPT_OK:
raise Exception('LTC.chacha_crypt() err = %d' % err)
raise Exception('LTC.chacha_crypt(), err = %d, "%s"' % (err, _err2str(err)))
return dataout.raw
# - - - - - - - - - - - - -
@ -254,9 +264,16 @@ if SHOW_CHACHA_EXAMPLE:
cha.set_iv32(iv)
cipher = cha.crypt(plain)
template = '\n ChaCha%d ciphertext for "%s" is "%s" \n'
template = '\n ChaCha%d ciphertext for "%s" is "%s"'
print template % (rounds, plain, cipher.encode('hex'))
# reset to decrypt
cha.set_iv32(iv)
decrypted = cha.crypt(cipher)
template = ' ChaCha%d decoded text for "%s" is "%s" \n'
print template % (rounds, plain, decrypted)
#---------------------------------------------------------------