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- # Ed25519 digital signatures
- # Based on http://ed25519.cr.yp.to/python/ed25519.py
- # See also http://ed25519.cr.yp.to/software.html
- # Adapted by Ron Garret
- # Sped up considerably using coordinate transforms found on:
- # http://www.hyperelliptic.org/EFD/g1p/auto-twisted-extended-1.html
- # Specifically add-2008-hwcd-4 and dbl-2008-hwcd
- try: # pragma nocover
- unicode
- PY3 = False
- def asbytes(b):
- """Convert array of integers to byte string"""
- return ''.join(chr(x) for x in b)
- def joinbytes(b):
- """Convert array of bytes to byte string"""
- return ''.join(b)
- def bit(h, i):
- """Return i'th bit of bytestring h"""
- return (ord(h[i//8]) >> (i%8)) & 1
- except NameError: # pragma nocover
- PY3 = True
- asbytes = bytes
- joinbytes = bytes
- def bit(h, i):
- return (h[i//8] >> (i%8)) & 1
- import hashlib
- b = 256
- q = 2**255 - 19
- l = 2**252 + 27742317777372353535851937790883648493
- def H(m):
- return hashlib.sha512(m).digest()
- def expmod(b, e, m):
- if e == 0: return 1
- t = expmod(b, e // 2, m) ** 2 % m
- if e & 1: t = (t * b) % m
- return t
- # Can probably get some extra speedup here by replacing this with
- # an extended-euclidean, but performance seems OK without that
- def inv(x):
- return expmod(x, q-2, q)
- d = -121665 * inv(121666)
- I = expmod(2,(q-1)//4,q)
- def xrecover(y):
- xx = (y*y-1) * inv(d*y*y+1)
- x = expmod(xx,(q+3)//8,q)
- if (x*x - xx) % q != 0: x = (x*I) % q
- if x % 2 != 0: x = q-x
- return x
- By = 4 * inv(5)
- Bx = xrecover(By)
- B = [Bx % q,By % q]
- #def edwards(P,Q):
- # x1 = P[0]
- # y1 = P[1]
- # x2 = Q[0]
- # y2 = Q[1]
- # x3 = (x1*y2+x2*y1) * inv(1+d*x1*x2*y1*y2)
- # y3 = (y1*y2+x1*x2) * inv(1-d*x1*x2*y1*y2)
- # return (x3 % q,y3 % q)
- #def scalarmult(P,e):
- # if e == 0: return [0,1]
- # Q = scalarmult(P,e/2)
- # Q = edwards(Q,Q)
- # if e & 1: Q = edwards(Q,P)
- # return Q
- # Faster (!) version based on:
- # http://www.hyperelliptic.org/EFD/g1p/auto-twisted-extended-1.html
- def xpt_add(pt1, pt2):
- (X1, Y1, Z1, T1) = pt1
- (X2, Y2, Z2, T2) = pt2
- A = ((Y1-X1)*(Y2+X2)) % q
- B = ((Y1+X1)*(Y2-X2)) % q
- C = (Z1*2*T2) % q
- D = (T1*2*Z2) % q
- E = (D+C) % q
- F = (B-A) % q
- G = (B+A) % q
- H = (D-C) % q
- X3 = (E*F) % q
- Y3 = (G*H) % q
- Z3 = (F*G) % q
- T3 = (E*H) % q
- return (X3, Y3, Z3, T3)
- def xpt_double (pt):
- (X1, Y1, Z1, _) = pt
- A = (X1*X1)
- B = (Y1*Y1)
- C = (2*Z1*Z1)
- D = (-A) % q
- J = (X1+Y1) % q
- E = (J*J-A-B) % q
- G = (D+B) % q
- F = (G-C) % q
- H = (D-B) % q
- X3 = (E*F) % q
- Y3 = (G*H) % q
- Z3 = (F*G) % q
- T3 = (E*H) % q
- return (X3, Y3, Z3, T3)
- def pt_xform (pt):
- (x, y) = pt
- return (x, y, 1, (x*y)%q)
- def pt_unxform (pt):
- (x, y, z, _) = pt
- return ((x*inv(z))%q, (y*inv(z))%q)
- def xpt_mult (pt, n):
- if n==0: return pt_xform((0,1))
- _ = xpt_double(xpt_mult(pt, n>>1))
- return xpt_add(_, pt) if n&1 else _
- def scalarmult(pt, e):
- return pt_unxform(xpt_mult(pt_xform(pt), e))
- def encodeint(y):
- bits = [(y >> i) & 1 for i in range(b)]
- e = [(sum([bits[i * 8 + j] << j for j in range(8)]))
- for i in range(b//8)]
- return asbytes(e)
- def encodepoint(P):
- x = P[0]
- y = P[1]
- bits = [(y >> i) & 1 for i in range(b - 1)] + [x & 1]
- e = [(sum([bits[i * 8 + j] << j for j in range(8)]))
- for i in range(b//8)]
- return asbytes(e)
-
- def publickey(sk):
- h = H(sk)
- a = 2**(b-2) + sum(2**i * bit(h,i) for i in range(3,b-2))
- A = scalarmult(B,a)
- return encodepoint(A)
- def Hint(m):
- h = H(m)
- return sum(2**i * bit(h,i) for i in range(2*b))
- def signature(m,sk,pk):
- h = H(sk)
- a = 2**(b-2) + sum(2**i * bit(h,i) for i in range(3,b-2))
- inter = joinbytes([h[i] for i in range(b//8,b//4)])
- r = Hint(inter + m)
- R = scalarmult(B,r)
- S = (r + Hint(encodepoint(R) + pk + m) * a) % l
- return encodepoint(R) + encodeint(S)
- def isoncurve(P):
- x = P[0]
- y = P[1]
- return (-x*x + y*y - 1 - d*x*x*y*y) % q == 0
- def decodeint(s):
- return sum(2**i * bit(s,i) for i in range(0,b))
- def decodepoint(s):
- y = sum(2**i * bit(s,i) for i in range(0,b-1))
- x = xrecover(y)
- if x & 1 != bit(s,b-1): x = q-x
- P = [x,y]
- if not isoncurve(P): raise Exception("decoding point that is not on curve")
- return P
- def checkvalid(s, m, pk):
- if len(s) != b//4: raise Exception("signature length is wrong")
- if len(pk) != b//8: raise Exception("public-key length is wrong")
- R = decodepoint(s[0:b//8])
- A = decodepoint(pk)
- S = decodeint(s[b//8:b//4])
- h = Hint(encodepoint(R) + pk + m)
- v1 = scalarmult(B,S)
- # v2 = edwards(R,scalarmult(A,h))
- v2 = pt_unxform(xpt_add(pt_xform(R), pt_xform(scalarmult(A, h))))
- return v1==v2
- ##########################################################
- #
- # Curve25519 reference implementation by Matthew Dempsky, from:
- # http://cr.yp.to/highspeed/naclcrypto-20090310.pdf
- # P = 2 ** 255 - 19
- P = q
- A = 486662
- #def expmod(b, e, m):
- # if e == 0: return 1
- # t = expmod(b, e / 2, m) ** 2 % m
- # if e & 1: t = (t * b) % m
- # return t
- # def inv(x): return expmod(x, P - 2, P)
- def add(n, m, d):
- (xn, zn) = n
- (xm, zm) = m
- (xd, zd) = d
- x = 4 * (xm * xn - zm * zn) ** 2 * zd
- z = 4 * (xm * zn - zm * xn) ** 2 * xd
- return (x % P, z % P)
- def double(n):
- (xn, zn) = n
- x = (xn ** 2 - zn ** 2) ** 2
- z = 4 * xn * zn * (xn ** 2 + A * xn * zn + zn ** 2)
- return (x % P, z % P)
- def curve25519(n, base=9):
- one = (base,1)
- two = double(one)
- # f(m) evaluates to a tuple
- # containing the mth multiple and the
- # (m+1)th multiple of base.
- def f(m):
- if m == 1: return (one, two)
- (pm, pm1) = f(m // 2)
- if (m & 1):
- return (add(pm, pm1, one), double(pm1))
- return (double(pm), add(pm, pm1, one))
- ((x,z), _) = f(n)
- return (x * inv(z)) % P
- import random
- def genkey(n=0):
- n = n or random.randint(0,P)
- n &= ~7
- n &= ~(128 << 8 * 31)
- n |= 64 << 8 * 31
- return n
- #def str2int(s):
- # return int(hexlify(s), 16)
- # # return sum(ord(s[i]) << (8 * i) for i in range(32))
- #
- #def int2str(n):
- # return unhexlify("%x" % n)
- # # return ''.join([chr((n >> (8 * i)) & 255) for i in range(32)])
- #################################################
- def dsa_test():
- import os
- msg = str(random.randint(q,q+q)).encode('utf-8')
- sk = os.urandom(32)
- pk = publickey(sk)
- sig = signature(msg, sk, pk)
- return checkvalid(sig, msg, pk)
- def dh_test():
- sk1 = genkey()
- sk2 = genkey()
- return curve25519(sk1, curve25519(sk2)) == curve25519(sk2, curve25519(sk1))
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