47 lines
1.5 KiB
Nim
47 lines
1.5 KiB
Nim
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# Stint
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# Copyright 2018 Status Research & Development GmbH
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# Licensed under either of
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#
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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#
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import ../stint, unittest, math
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suite "Modular arithmetic":
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test "Modular addition":
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# uint16 rolls over at 65535
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let a = 50000.stuint(16)
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let b = 20000.stuint(16)
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let m = 60000.stuint(16)
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check: addmod(a, b, m) == 10000.stuint(16)
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test "Modular substraction":
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let a = 5.stuint(16)
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let b = 7.stuint(16)
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let m = 20.stuint(16)
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check: submod(a, b, m) == 18.stuint(16)
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test "Modular multiplication":
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# https://www.wolframalpha.com/input/?i=(1234567890+*+987654321)+mod+999999999
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# --> 345_679_002
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let a = 1234567890.stuint(64)
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let b = 987654321.stuint(64)
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let m = 999999999.stuint(64)
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check: mulmod(a, b, m) == 345_679_002.stuint(64)
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test "Modular exponentiation":
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# https://www.khanacademy.org/computing/computer-science/cryptography/modarithmetic/a/fast-modular-exponentiation
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check:
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powmod(5.stuint(16), 117.stuint(16), 19.stuint(16)) == 1.stuint(16)
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powmod(3.stuint(16), 1993.stuint(16), 17.stuint(16)) == 14.stuint(16)
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check:
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powmod(12.stuint(256), 34.stuint(256), high(UInt256)) == "4922235242952026704037113243122008064".u256
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