- § Cryptography
- Electronic Codebook (ECB) is the simplest Block cipher mode of operation.
- Split input into blocks, each block is independently encrypted with the same key.
- The weakness is that same blocks would produce the same results. Thus, ECB does not hide data patterns.
- ECB is also susceptible to Replay attack because each block is decrypted in exactly the same way.
- It is not recommended to use ECB in cryptographic protocols at all.
Inability to hide data patterns is very striking on images with large monotonic colors. Input:
Encrypted with ECB:
(while every color is encrypted, the overall image pattern is very visible)
Compare this with CBC (or other mode):
(Note that if image looks random to the eye, that does not mean it is securely encrypted)