Created
March 30, 2018 12:40
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[Modular Inverse] #crypto #math
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| def egcd(a, b): | |
| if a == 0: | |
| return (b, 0, 1) | |
| else: | |
| g, y, x = egcd(b % a, a) | |
| return (g, x - (b // a) * y, y) | |
| def modinv(a, m): | |
| g, x, y = egcd(a, m) | |
| if g != 1: | |
| raise Exception('modular inverse does not exist') | |
| else: | |
| return x % m |
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