[Cryptology] CFB(Cipher FeedBack) mode

□ CFB(Cipher FeedBack) mode

○ CFB Encryption : XOR(En(C[i-1]), P[i])

- Encryption(IV(initialization vector)) → XOR(Encryption result, First plaintext block(P[1])) → First ciphertext block(C[1])
- Encryption(Previous ciphertext block(C[i-1])) → XOR(Encryption result, Current plaintext block(P[i])) → Current ciphertext block(C[i])

○ CFB Decryption : XOR(En(C[i-1]), C[i])

- Encryption(IV(initialization vector)) → XOR(Encryption result, First ciphertext block(C[1])) → First plaintext block(P[1])
- Encryption(Previous ciphertext block(C[i-1])) → XOR(Encryption result, Current Encryption block(C[i])) → Current plaintext block(P[i])

○ Characteristic

- Encryption : If plaintext block(P[i]) is damaged, from now on, all ciphertext blocks(C[i], C[i+1] ...) are damaged
- Decryption : if cipher block(C[i]) is damaged, current plaintext block(P[i]) and next plaintext block(P[i+1]) is damaged
- Encryption(decryption x) is used in the CFB Decryption

P.S. Symbol information

- En:Encryption / De:Decryption
- C:Cipher text / P:Plain text
- i:Each step(Ex. Current step:i / one Previous step:i-1 / one Next step:i+1)