decrypt = rsa.decrypt_string(ciphertext, R)
print
print "Bob gets this message:", decrypt
#### Eve
# Calculate products of the moduli (pubkeys) EXCEPT pubkey number i.
ms = [None] * k
for i in range(k):
x = copy.copy(n)
del x[i]
ms[i] = reduce(lambda a, b: a * b, x)
# Work thru Chinese Remainder Theorem
result = 0
for i in range(k):
result += c[i] * ms[i] * rsa.invmod(ms[i], n[i])
result = result % reduce(lambda a, b: a * b, n)
# Get final text
overheard = rsa.i2s(cuberoot(result))
print "Eve hears this message:", overheard
#### tests ####
assert message == decrypt
assert message == overheard
assert decrypt == overheard
warn("Passed assertions:", __file__)
print "Along with signature..."
print signature
print "Does it verify?"
print verify(signature, message, U)
print
#### Forging
msg_to_forge = "hi mom"
hash_mom = sha1(msg_to_forge).digest()
block_mom = ("\x00\x01\xff\xff\x00ASN.1" +
chr(len(hash_mom)) +
hash_mom)
bytes_to_add = (bits / 8) - len(block_mom)
block_mom += "\x00" * bytes_to_add
block_mom_cube = "\x00" + rsa.i2s(cuberoot(rsa.s2i(block_mom)) ** 3)
forged_sig = cuberoot(rsa.s2i(block_mom_cube))
#### Check the sig
print "A poor fool received message:", msg_to_forge
print "Along with signature..."
print forged_sig
print "Does it verify?"
result = verify(forged_sig, msg_to_forge, U)
print result
print
#### tests ####
assert result
assert unpad(pkcs_1_5("Hello", 1024)) == "Hello"
decrypt = rsa.decrypt_string(ciphertext, R)
print
print "Bob gets this message:", decrypt
#### Eve
# Calculate products of the moduli (pubkeys) EXCEPT pubkey number i.
ms = [None]*k
for i in range(k):
x = copy.copy(n)
del x[i]
ms[i] = reduce(lambda a, b: a*b, x)
# Work thru Chinese Remainder Theorem
result = 0
for i in range(k):
result += c[i] * ms[i] * rsa.invmod(ms[i], n[i])
result = result % reduce(lambda a, b: a*b, n)
# Get final text
overheard = rsa.i2s(cuberoot(result))
print "Eve hears this message:", overheard
#### tests ####
assert message == decrypt
assert message == overheard
assert decrypt == overheard
warn("Passed assertions:", __file__)
