mirror of
https://github.com/elseif/MikroTikPatch.git
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49 lines
1.7 KiB
Python
49 lines
1.7 KiB
Python
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#
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# toyecc - A small Elliptic Curve Cryptography Demonstration.
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# Copyright (C) 2011-2022 Johannes Bauer
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#
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# This file is part of toyecc.
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#
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# toyecc is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; this program is ONLY licensed under
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# version 3 of the License, later versions are explicitly excluded.
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#
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# toyecc is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with toyecc; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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# Johannes Bauer <JohannesBauer@gmx.de>
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#
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def secure_rand(length):
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import os
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"""Returns a secure random bytes() object of the length 'length' bytes."""
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data = os.urandom(length)
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assert(len(data) == length)
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return data
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def secure_rand_int(max_value):
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"""Yields a value 0 <= return < maxvalue."""
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assert(max_value >= 2)
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bytecnt = ((max_value - 1).bit_length() + 7) // 8
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max_bin_value = 256 ** bytecnt
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wholecnt = max_bin_value // max_value
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cutoff = wholecnt * max_value
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while True:
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rnd = sum((value << (8 * bytepos)) for (bytepos, value) in enumerate(secure_rand(bytecnt)))
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if rnd < cutoff:
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break
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return rnd % max_value
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def secure_rand_int_between(min_value, max_value):
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"""Yields a random number which goes from min_value (inclusive) to
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max_value (inclusive)."""
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return secure_rand_int(max_value - min_value + 1) + min_value
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