def encrypt(plaintext_file_name, ciphertext_file_name, exp, n, block_size):
cipher_file = open(ciphertext_file_name, "w")
# Generate a random one-time pad.
pad = generate_pad(block_size)
# Convert the one-time pad to a long so that it can be encrypted with RSA.
pad_as_long = string_to_long(pad)
# Encrypt the one-time pad using RSA.
encrypted_pad = modular_exponentiation(pad_as_long, exp, n)
# Write the encrypted one-time pad to the ciphertext file, followed by a newline.
cipher_file.write(str(encrypted_pad) + "\n")
plaintext_file = open(plaintext_file_name, "rb")
while True:
# Read the next block of the plaintext file.
plaintext_block = plaintext_file.read(block_size)
if len(plaintext_block) == 0:
break # done if no characters left to read
else:
cipher_file.write(xor_block(pad, plaintext_block))
cipher_file.close()
plaintext_file.close()
def decrypt(ciphertext_file_name, decrypted_file_name, exp, n, block_size):
cipher_file = open(ciphertext_file_name, "rb")
# Read the encrypted one-time pad a character at a time, until hitting the newline.
encrypted_pad_text = ""
while True:
digit = cipher_file.read(1)
if digit == "\n":
break
else:
encrypted_pad_text += digit
# Convert the encrypted one-time pad to a long int so that it can be decrypted with RSA.
encrypted_pad = long(encrypted_pad_text)
# Decrypt the one-time pad with RSA.
pad_as_long = modular_exponentiation(encrypted_pad, exp, n)
# Convert the one-time pad to a string of bytes.
pad = long_to_string(pad_as_long, block_size)
decrypted_file = open(decrypted_file_name, "w")
while True:
# Process the next block of the ciphertext.
ciphertext_block = cipher_file.read(block_size)
if len(ciphertext_block) == 0:
break # done when no ciphertext characters remain
else:
decrypted_file.write(xor_block(pad, ciphertext_block))
cipher_file.close()
decrypted_file.close()
def encrypt(plaintext_file_name, ciphertext_file_name, exp, n, block_size):
cipher_file = open(ciphertext_file_name, "w")
# Generate a random one-time pad.
pad = generate_pad(block_size)
# Convert the one-time pad to an int so that it can be encrypted with RSA.
pad_as_int = str_to_int(pad)
# Encrypt the one-time pad using RSA.
encrypted_pad = modular_exponentiation(pad_as_int, exp, n)
# Write the encrypted one-time pad to the ciphertext file, followed by a newline.
cipher_file.write(str(encrypted_pad) + "\n")
plaintext_file = open(plaintext_file_name, "rb")
while True:
# Read the next block of the plaintext file.
plaintext_block = plaintext_file.read(block_size)
if len(plaintext_block) == 0:
break # done if no characters left to read
else:
# Construct a block of ciphertext.
ciphertext_block = ""
# XOR each byte in the plaintext block with a byte from the one-time pad,
# and concatenate it to the ciphertext block.
for i in range(len(plaintext_block)):
ciphertext_block += chr(ord(plaintext_block[i]) ^ ord(pad[i]))
cipher_file.write(ciphertext_block)
cipher_file.close()
plaintext_file.close()
def decrypt(ciphertext_file_name, decrypted_file_name, exp, n, block_size):
cipher_file = open(ciphertext_file_name, "rb")
# Read the encrypted one-time pad a character at a time, until hitting the newline.
encrypted_pad_text = ""
while True:
digit = cipher_file.read(1)
if digit == "\n":
break
else:
encrypted_pad_text += digit
# Convert the encrypted one-time pad to an int so that it can be decrypted with RSA.
encrypted_pad = int(encrypted_pad_text)
# Decrypt the one-time pad with RSA.
pad_as_int = modular_exponentiation(encrypted_pad, exp, n)
# Convert the one-time pad to a string of bytes.
pad = int_to_str(pad_as_int, block_size)
decrypted_file = open(decrypted_file_name, "w")
while True:
# Process the next block of the ciphertext.
ciphertext_block = cipher_file.read(block_size)
if len(ciphertext_block) == 0:
break # done when no ciphertext characters remain
else:
# Construct a block of decrypted plaintext.
decrypted_block = ""
# XOR each byte in the ciphertext block with a byte from the one-time pad,
# and concatenate it to the decrypted plaintext block.
for i in range(len(ciphertext_block)):
decrypted_block += chr(ord(ciphertext_block[i]) ^ ord(pad[i]))
decrypted_file.write(decrypted_block)
cipher_file.close()
decrypted_file.close()
def fermat_test(m):
return modular_exponentiation(2, m-1, m) == 1
def fermat_test(m):
return modular_exponentiation(2, m - 1, m) == 1