An AES implementation of a CTR block cipher using a CBC-MAC along with an ECB implementation for comparison.
In the libdcrypt directory, run
$ ./configure
After successful configuration build the executables by running
$ make
Now the AES Pseudo Random Permutation is avaliable for use in the src executables. Finally in src run
$ make
In the src directory, run
$ ./keygen keyfile
to generate a 64-bit key saved to keyfile. To encrypt, run
$ ./ctr_encrypt keyfile plaintext ciphertext
to encrypt the content of plaintext to a file named ciphertext. To decrypt, run
$ ./ctr_decrypt keyfile ciphertext plaintext
to decrypt the content of ciphertext to a file named plaintext.
Likewise use ecb instead of ctr to encrypt using the Electronic Code Book (ECB) mode of operation for the AES block cipher instead of the Counter (CTR) mode of operation. Note that the CTR mode is Chosen Plaintext Attack (CPA) secure while the ECB mode is not. Also the CTR mode implementation includes a Cipher Block Chaining Message Authentication Code (CBC-MAC) along with the standard encryption to upgrade the scheme from CPA secure to Chosen Ciphertext Attack (CCA) secure making the ctr suite secure against man-in-the-middle tampering to the ciphertext. Thus the ctr suite is more secure and desirable than the ecb suite.
In the examples directory there are bitmap images encrypted with both ctr mode and ecb mode to show how inferior ecb is when encrypting files. Notice that the circles.bmp image is still very clear with ecb due to no randomization of state tracking in the mode making the encryption not CPA secure. The ctr mode is CPA secure and CCA secure (due to the CBC-MAC) making the bmp image encryption appear much more "random".
- Alex Masi
- Walter Krawec
- Thank you:
- Professor Walter Krawec
- Libdcrypt
- Originally created for an Honor's Conversion in CSE 4702: Intro to Modern Cryptography at the University of Connecticut taught by Professor Walter Krawec.