PyCrypto RSA failing for long strings

Question

I'm trying to use RSA with PyCrypto to encrypt/decrypt a long string. I am quite confident that my code works for short strings (to about 200 characters), but for strings longer than that, I cannot successfully decrypt.

This is what I have:

random_generator = Random.new().read

def encrypt_RSA(message):
    key = open('public_key.der', "r").read()
    rsakey = RSA.importKey(key)
    encrypted = rsakey.encrypt(message, random_generator)
    return encrypted

def decrypt_RSA(package):
    key = open('private_key.der', "r").read() 
    rsakey = RSA.importKey(key)
    decrypted = rsakey.decrypt(package) 
    return decrypted

alphabet = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'
small_alphabet = 'abcdefghijklmnopqrstuvwxyz'

encrypted = encrypt_RSA(small_alphabet)
print base64.b64encode(encrypted[0])
print "========================"
print decrypt_RSA(encrypted[0])

This works for the string small_alphabet, but not alphabet. Why is that?

I'm using PyCrypto 2.6.1, Python 2.7.6.

PyCrypto RSA failing for long strings

0 Answers0