def bleichenbacher(ciphertext):
"""
Perform Bleichenbacher attack as described in his paper.
"""
# Step 1. is only needed when the ciphertext is
# not PKCS1 conforming
# integer value of ciphertext
c = utils.bytes_to_integer(ciphertext)
B = 2**(8 * (k - 2))
M = [Interval(2 * B, 3 * B - 1)]
# Step 2.A.
s = find_smallest_s(ceil(n, 3 * B), c)
M = update_intervals(M, s, B)
while True:
# Step 2.B.
if len(M) >= 2:
s = find_smallest_s(s + 1, c)
# Step 2.C.
elif len(M) == 1:
a, b = M[0]
# Step 4.
if a == b:
return utils.integer_to_bytes(a % n)
s = find_s_in_range(a, b, s, B, c)
M = update_intervals(M, s, B)
def decrypt_string(secret_key, ciphertext):
enc_integer = utils.bytes_to_integer(ciphertext)
integer = decrypt_integer(secret_key, enc_integer)
message = utils.integer_to_bytes(integer)
return message
def encrypt_string(public_key, message):
integer = utils.bytes_to_integer(message)
enc_integer = encrypt_integer(public_key, integer)
enc_string = utils.integer_to_bytes(enc_integer)
return enc_string