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Added a few speed-ups to the DES code

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Marshall T. Vandegrift 2008-07-19 16:45:41 -04:00
parent 2faf9ef606
commit 731631a7d7
1 changed files with 23 additions and 15 deletions
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38
src/calibre/ebooks/lit/msdes.py
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@ -1,6 +1,7 @@
# Re-modified for use in MS LIT decryption. Un-reversed the bytebit[] array.
# Substituted Microsoft's absurd modified S-boxes. Modified the encrypt/decrypt
# methods to handle more than one block at a time.
# Substituted Microsoft's absurd modified S-boxes. Modified the
# encrypt/decrypt methods to handle more than one block at a time. Added a few
# speed-ups supported by modern versions of Python. Added option 'psyco' use.
#
# And lo, all the previous notices follow:
@ -125,30 +126,30 @@ class DesCipher:
pcr = [0]*56 #new int[56];
kn = [0]*32 #new int[32];
for j in range(56):
for j in xrange(56):
l = pc1[j]
m = l & 07
pc1m[j] = ((keyBlock[l >> 3] & bytebit[m]) != 0)
for i in range(16):
for i in xrange(16):
if encrypting:
m = i << 1
else:
m = (15-i) << 1
n = m + 1
kn[m] = kn[n] = 0
for j in range(28):
for j in xrange(28):
l = j + totrot[i]
if l < 28:
pcr[j] = pc1m[l]
else:
pcr[j] = pc1m[l - 28]
for j in range(28, 56):
for j in xrange(28, 56):
l = j + totrot[i]
if l < 56:
pcr[j] = pc1m[l]
else:
pcr[j] = pc1m[l - 28]
for j in range(24):
for j in xrange(24):
if pcr[pc2[j]] != 0:
kn[m] |= bigbyte[j]
if pcr[pc2[j+24]] != 0:
@ -163,7 +164,7 @@ class DesCipher:
rawi = 0
KnLi = 0
for i in range(16):
for i in xrange(16):
raw0 = raw[rawi]
rawi += 1
raw1 = raw[rawi]
@ -187,11 +188,10 @@ class DesCipher:
if len(clearText) % 8 != 0:
raise TypeError, "length must be multiple of block size"
result = []
while clearText:
for base in xrange(0, len(clearText), 8):
result.append(struct.pack(
">LL", *self.des(struct.unpack(">LL", clearText[:8]),
">LL", *self.des(struct.unpack(">LL", clearText[base:base+8]),
self.encryptKeys)))
clearText = clearText[8:]
return ''.join(result)
#/ Decrypt a block of eight bytes.
@ -199,11 +199,10 @@ class DesCipher:
if len(cipherText) % 8 != 0:
raise TypeError, "length must be multiple of block size"
result = []
while cipherText:
for base in xrange(0, len(cipherText), 8):
result.append(struct.pack(
">LL", *self.des(struct.unpack(">LL", cipherText[:8]),
">LL", *self.des(struct.unpack(">LL", cipherText[base:base+8]),
self.decryptKeys)))
cipherText = cipherText[8:]
return ''.join(result)
# The DES function.
@ -234,7 +233,7 @@ class DesCipher:
right ^= work
leftt = ((leftt << 1) | ((leftt >> 31) & 1)) & 0xffffffffL
for round in range(8):
for round in xrange(8):
work = ((right << 28) | (right >> 4)) & 0xffffffffL
work ^= keys[keysi]
keysi += 1
@ -322,6 +321,7 @@ pc2 = [
45, 41, 49, 35, 28, 31,
]
# Microsoft's modified S-boxes for LIT file encryption
SP1 = [
0x02080800L, 0x00080000L, 0x02000002L, 0x02080802L,
0x02000000L, 0x00080802L, 0x00080002L, 0x02000002L,
@ -473,6 +473,14 @@ def new(key):
block_size = 8
key_size = 8
try:
import psyco
psyco.bind(DesCipher.deskey)
psyco.bind(DesCipher.cookey)
psyco.bind(DesCipher.des)
except ImportError:
pass
#test only:
if __name__ == '__main__':
des = DesCipher("\x01\x23\x45\x67\x89\xab\xcd\xef")