def forgeSignature(pub, message):
sha1 = hashlib.sha1()
sha1.update(message)
digest = sha1.digest()
block = b'\x00\x01\xff\x00' + digest + (b'\x00' * (128 - len(digest) - 4))
blocknum = challenge39.bytestonum(block)
signaturenum = challenge40.floorRoot(blocknum, 3) + 1
signature = challenge39.numtobytes(signaturenum)
return signature
def forgeSignature(pub, message):
sha1 = hashlib.sha1()
sha1.update(message)
digest = sha1.digest()
block = b'\x00\x01\xff\x00' + digest + (b'\x00' * (128 - len(digest) - 4))
(d, n) = pub
blocknum = challenge39.bytestonum(block)
signaturenum = challenge40.floorRoot(blocknum, 3) + 1
signature = challenge39.numtobytes(signaturenum)
return signature
def deducePlaintext(ciphertext, pub, parityOracle):
e, n = pub
k = (n.bit_length() + 7) // 8
B = 2**(8*(k-2))
c0 = challenge39.bytestonum(ciphertext)
M = [(2*B, 3*B - 1)]
(s, c) = computeFirstS(e, n, B, c0, parityOracle)
M = getNextInterval(n, M, s, B)
while True:
if len(M) == 1 and M[0][0] == M[0][1]:
m = M[0][0]
return b'\x00' + challenge39.numtobytes(m)
(s, c) = computeNextS(e, n, M, s, B, c0)
M = getNextInterval(n, M, s, B)
def deducePlaintext(ciphertext, pub, parityOracle):
(e, n) = pub
low = 0
high = 1
denom = 1
c = challenge39.bytestonum(ciphertext)
k = pow(2, e, n)
for _ in range(n.bit_length()):
c = (c * k) % n
p = parityOracle(c)
d = high - low
low *= 2
high *= 2
denom *= 2
if p == 0:
high -= d
else:
low += d
hightext = challenge39.numtobytes(n * high // denom)
print(hightext)
return hightext
import challenge39 import binascii import math (pub0, priv0) = challenge39.genKey(256) (pub1, priv1) = challenge39.genKey(256) (pub2, priv2) = challenge39.genKey(256) plaintext = b'This is a plaintext string' plainnum = challenge39.bytestonum(plaintext) c0 = challenge39.encryptnum(pub0, plainnum) c1 = challenge39.encryptnum(pub1, plainnum) c2 = challenge39.encryptnum(pub2, plainnum) n0 = pub0[1] n1 = pub1[1] n2 = pub2[1] ms0 = n1 * n2 ms1 = n0 * n2 ms2 = n0 * n1 N = n0 * n1 * n2 r0 = (c0 * ms0 * challenge39.invmod(ms0, n0)) r1 = (c1 * ms1 * challenge39.invmod(ms1, n1)) r2 = (c2 * ms2 * challenge39.invmod(ms2, n2)) r = (r0 + r1 + r2) % N
def decryptOnce(ciphertext):
sha1 = hashlib.sha1()
sha1.update(ciphertext)
digest = sha1.digest()
if digest in decryptedHashes:
raise ValueError('Already decrypted')
decryptedHashes.add(digest)
return challenge39.decryptbytes(priv, ciphertext)
if __name__ == '__main__':
plaintext = b'secret text'
ciphertext = encrypt(plaintext)
plaintext2 = decryptOnce(ciphertext)
if plaintext2 != plaintext:
raise ValueError(plaintext2 + b' != ' + plaintext)
(e, n) = pub
s = random.randint(2, n - 1)
c = challenge39.bytestonum(ciphertext)
c2 = (pow(s, e, n) * c) % n
ciphertext2 = challenge39.numtobytes(c2)
plaintext3 = decryptOnce(ciphertext2)
p3 = challenge39.bytestonum(plaintext3)
p4 = (p3 * challenge39.invmod(s, n)) % n
plaintext4 = challenge39.numtobytes(p4)
if plaintext4 != plaintext:
raise ValueError(plaintext4 + b' != ' + plaintext)
return challenge39.encryptbytes(pub, plaintext)
def decryptOnce(ciphertext):
sha1 = hashlib.sha1()
sha1.update(ciphertext)
digest = sha1.digest()
if digest in decryptedHashes:
raise ValueError('Already decrypted')
decryptedHashes.add(digest)
return challenge39.decryptbytes(priv, ciphertext)
if __name__ == '__main__':
plaintext = b'secret text'
ciphertext = encrypt(plaintext)
plaintext2 = decryptOnce(ciphertext)
if plaintext2 != plaintext:
raise ValueError(plaintext2 + b' != ' + plaintext)
(e, n) = pub
s = random.randint(2, n - 1)
c = challenge39.bytestonum(ciphertext)
c2 = (pow(s, e, n) * c) % n
ciphertext2 = challenge39.numtobytes(c2)
plaintext3 = decryptOnce(ciphertext2)
p3 = challenge39.bytestonum(plaintext3)
p4 = (p3 * challenge39.invmod(s, n)) % n
plaintext4 = challenge39.numtobytes(p4)
if plaintext4 != plaintext:
raise ValueError(plaintext4 + b' != ' + plaintext)
import challenge39 import binascii import math (pub0, priv0) = challenge39.genKey(256) (pub1, priv1) = challenge39.genKey(256) (pub2, priv2) = challenge39.genKey(256) plaintext = b'This is a plaintext string' plainnum = challenge39.bytestonum(plaintext) c0 = challenge39.encryptnum(pub0, plainnum) c1 = challenge39.encryptnum(pub1, plainnum) c2 = challenge39.encryptnum(pub2, plainnum) n0 = pub0[1] n1 = pub1[1] n2 = pub2[1] ms0 = n1 * n2 ms1 = n0 * n2 ms2 = n0 * n1 N = n0 * n1 * n2 r0 = (c0 * ms0 * challenge39.invmod(ms0, n0)) r1 = (c1 * ms1 * challenge39.invmod(ms1, n1)) r2 = (c2 * ms2 * challenge39.invmod(ms2, n2)) r = (r0 + r1 + r2) % N
