DES

DES

1. 5 modes

   • Electronic Codebook Mode (ECB): encrypts with key
   • Cipher Block Chaining (CBC): eack block of text XORed with preceding block
   • Cipher Feedback (CFB): fills up buffers with message and encrypts each buffer. Uses an IV and chaining.
   • Output Feedback (OFB): XORs plaintext with a seed value
   • Counter mode (CTR): instead of creating a seed value for each encryption / decryption, it uses a simple counter that increments for each

2. Triple DES (3DES)

   • 4 versions
     • DES-EE3 mode's key length is 168 and encrypts three times
     • DES-EDE3: uses 3 keys like DES-EDE3, but encrypts, decrypts, then encrypts instead
     • DES-EEE2 uses two keys to encrypt thrice

3. 56-bit key