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'''Core mathematical operations.
This is the actual core RSA implementation, which is only defined
mathematically on integers.
'''
import types
import rsa.common
def encrypt_int(message, ekey, n):
"""Encrypts a message using encryption key 'ekey', working modulo n"""
if type(message) is types.IntType:
message = long(message)
if not type(message) is types.LongType:
raise TypeError("You must pass a long or int")
if message < 0 or message > n:
raise OverflowError("The message is too long")
#Note: Bit exponents start at zero (bit counts start at 1) this is correct
safebit = rsa.common.bit_size(n) - 2 #compute safe bit (MSB - 1)
message += (1 << safebit) #add safebit to ensure folding
return pow(message, ekey, n)
def decrypt_int(cyphertext, dkey, n):
"""Decrypts a cypher text using the decryption key 'dkey', working
modulo n"""
message = pow(cyphertext, dkey, n)
safebit = rsa.common.bit_size(n) - 2 #compute safe bit (MSB - 1)
message -= (1 << safebit) #remove safebit before decode
return message
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