Create software that can encrypt and decrypt in 4-bit cipher feedback mode using one of the following ciphers: additive modulo 256, affine modulo 256, S-DES;

or

8-bit cipher feedback mode using one of the following ciphers: 2 * 2 Hill modulo 256. Test data for S-DES using a binary initialization vector of 1010 1011. A binary plaintext of 0001 0010 0011 0100 encrypted with a binary key of 01111 11101 should give a binary plaintext of 1110 1100 1111 1010. Decryption should work correspondingly.