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# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Core mathematical operations.
This is the actual core RSA implementation, which is only defined
mathematically on integers.
"""
def assert_int(var: int, name: str) -> None:
if isinstance(var, int):
return
raise TypeError("%s should be an integer, not %s" % (name, var.__class__))
def encrypt_int(message: int, ekey: int, n: int) -> int:
"""Encrypts a message using encryption key 'ekey', working modulo n"""
assert_int(message, "message")
assert_int(ekey, "ekey")
assert_int(n, "n")
if message < 0:
raise ValueError("Only non-negative numbers are supported")
if message > n:
raise OverflowError("The message %i is too long for n=%i" % (message, n))
return pow(message, ekey, n)
def decrypt_int(cyphertext: int, dkey: int, n: int) -> int:
"""Decrypts a cypher text using the decryption key 'dkey', working modulo n"""
assert_int(cyphertext, "cyphertext")
assert_int(dkey, "dkey")
assert_int(n, "n")
message = pow(cyphertext, dkey, n)
return message
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