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71 lines
1.7 KiB
Python
71 lines
1.7 KiB
Python
from binascii import hexlify, unhexlify
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from os import urandom
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def read_key_from_file(file):
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f = open(file)
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n_str = f.readline()[:-1]
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e_str = f.readline()[:-1]
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p_str = f.readline()[:-1]
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q_str = f.readline()[:-1]
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f.close()
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e = int(e_str, 16)
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p = int(p_str, 16)
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q = int(q_str, 16)
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n = int(n_str, 16)
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if n != p * q:
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raise ValueError("wrong key", p, q, n)
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return (unhexlify(n_str), unhexlify(e_str), unhexlify(p_str), unhexlify(q_str), e, p, q, n)
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# egcd and modinv are from wikibooks
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# https://en.wikibooks.org/wiki/Algorithm_Implementation/Mathematics/Extended_Euclidean_algorithm
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def egcd(a, b):
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if a == 0:
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return (b, 0, 1)
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else:
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g, y, x = egcd(b % a, a)
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return (g, x - (b // a) * y, y)
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def modinv(a, m):
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g, x, y = egcd(a, m)
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if g != 1:
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raise Exception('modular inverse does not exist')
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else:
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return x % m
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def pkcs1_pad_for_sign(digestinfo):
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byte_repr = b'\x00' + b'\x01' \
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+ bytes.ljust(b'', 256 - 19 - 32 - 3, b'\xff') \
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+ b'\x00' + digestinfo
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return int(hexlify(byte_repr), 16)
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def compute_signature(key, digestinfo):
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e = key[4]
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p = key[5]
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q = key[6]
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n = key[7]
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p1 = p - 1
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q1 = q - 1
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h = p1 * q1
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d = modinv(e, h)
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dp = d % p1
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dq = d % q1
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qp = modinv(q, p)
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input = pkcs1_pad_for_sign(digestinfo)
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t1 = pow(input, dp, p)
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t2 = pow(input, dq, q)
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t = ((t1 - t2) * qp) % p
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sig = t2 + t * q
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return sig
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def integer_to_bytes_256(i):
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s = hex(i)[2:]
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s = s.rstrip('L')
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if len(s) & 1:
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s = '0' + s
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return bytes.rjust(unhexlify(s), 256, b'\x00')
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def get_raw_pubkey(key):
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return key[0]
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