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