□ OFB(Output FeedBack) mode
○ OFB Encryption : XOR(En(IV)[i], P[i])
- Encryption(IV(Initialization Vector)) → XOR(Encryption result, First plaintext block(P[1])) → First ciphertext block(C[1])
- Encryption(Previous encryption result(En(IV)[i-1])) → XOR(Encryption result, Current plaintext block(P[i])) → Current ciphertext block(C[i])
○ OFB Decryption : XOR(En(IV)[i], C[i])- Encryption(Previous encryption result(En(IV)[i-1])) → XOR(Encryption result, Current plaintext block(P[i])) → Current ciphertext block(C[i])
- Encryption(IV(Initialization Vector)) → XOR(Encryption result, First ciphertext block(C[1])) → First plaintext block(P[1])
- Encryption(Previous encryption result(En(IV)[i-1])) → XOR(Encryption result, Current ciphertext block(C[i])) → Current plaintext block(P[i])
○ Characteristic- Encryption(Previous encryption result(En(IV)[i-1])) → XOR(Encryption result, Current ciphertext block(C[i])) → Current plaintext block(P[i])
- Encryption/Decryption : If Plaintext/Ciphertext block is damaged, only ciphertext block in the present step is damaged
- Encryption, decryption method is same
- Encryption, decryption method is same
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)
- C:Cipher text / P:Plain text
- i:Each step(Ex. Current step:i / one Previous step:i-1 / one Next step:i+1)
