AES-256-OFB ENCRYPTION TOOL
Other Crypto Algorithms
AES-128-CBC AES-128-CBC-CTS AES-128-CBC-HMAC-SHA1 AES-128-CBC-HMAC-SHA256 AES-128-CCM AES-128-CFB AES-128-CFB1 AES-128-CFB8 AES-128-CTR AES-128-ECB AES-128-GCM AES-128-GCM-SIV AES-128-OCB AES-128-OFB AES-128-SIV AES-128-WRAP AES-128-WRAP-INV AES-128-WRAP-PAD AES-128-WRAP-PAD-INV AES-128-XTS AES-192-CBC AES-192-CBC-CTS AES-192-CCM AES-192-CFB AES-192-CFB1 AES-192-CFB8 AES-192-CTR AES-192-ECB AES-192-GCM AES-192-GCM-SIV AES-192-OCB AES-192-OFB AES-192-SIV AES-192-WRAP AES-192-WRAP-INV AES-192-WRAP-PAD AES-192-WRAP-PAD-INV AES-256-CBC AES-256-CBC-CTS AES-256-CBC-HMAC-SHA1 AES-256-CBC-HMAC-SHA256 AES-256-CCM AES-256-CFB AES-256-CFB1 AES-256-CFB8 AES-256-CTR AES-256-ECB AES-256-GCM AES-256-GCM-SIV AES-256-OCB AES-256-OFB AES-256-SIV AES-256-WRAP AES-256-WRAP-INV AES-256-WRAP-PAD AES-256-WRAP-PAD-INV AES-256-XTS ARIA-128-CBC ARIA-128-CCM ARIA-128-CFB ARIA-128-CFB1 ARIA-128-CFB8 ARIA-128-CTR ARIA-128-ECB ARIA-128-GCM ARIA-128-OFB ARIA-192-CBC ARIA-192-CCM ARIA-192-CFB ARIA-192-CFB1 ARIA-192-CFB8 ARIA-192-CTR ARIA-192-ECB ARIA-192-GCM ARIA-192-OFB ARIA-256-CBC ARIA-256-CCM ARIA-256-CFB ARIA-256-CFB1 ARIA-256-CFB8 ARIA-256-CTR ARIA-256-ECB ARIA-256-GCM ARIA-256-OFB CAMELLIA-128-CBC CAMELLIA-128-CBC-CTS CAMELLIA-128-CFB CAMELLIA-128-CFB1 CAMELLIA-128-CFB8 CAMELLIA-128-CTR CAMELLIA-128-ECB CAMELLIA-128-OFB CAMELLIA-192-CBC CAMELLIA-192-CBC-CTS CAMELLIA-192-CFB CAMELLIA-192-CFB1 CAMELLIA-192-CFB8 CAMELLIA-192-CTR CAMELLIA-192-ECB CAMELLIA-192-OFB CAMELLIA-256-CBC CAMELLIA-256-CBC-CTS CAMELLIA-256-CFB CAMELLIA-256-CFB1 CAMELLIA-256-CFB8 CAMELLIA-256-CTR CAMELLIA-256-ECB CAMELLIA-256-OFB CHACHA20 CHACHA20-POLY1305 DES-EDE-CBC DES-EDE-CFB DES-EDE-ECB DES-EDE-OFB DES-EDE3-CBC DES-EDE3-CFB DES-EDE3-CFB1 DES-EDE3-CFB8 DES-EDE3-ECB DES-EDE3-OFB DES3-WRAPThe AES-256-OFB algorithm is a symmetric-key block cipher that operates with a fixed block size of 128 bits and a key size of 256 bits. The algorithm is based on the Advanced Encryption Standard (AES) and uses the Output Feedback (OFB) mode to transform the block cipher into a synchronous stream cipher. In this configuration, the encryption and decryption processes are identical, relying on the generation of a keystream that is XORed with plaintext or ciphertext.
Key Components
The algorithm requires three primary components for operation: a 256-bit secret key, a 128-bit initialization vector (IV), and the plaintext or ciphertext data. The key undergoes an expansion process to generate a series of round keys used in the AES rounds. The IV is used to initialize the OFB mode and ensures that repeated encryptions with the same key produce distinct ciphertexts.
Encryption Process
During encryption, the IV is first encrypted using AES-256 to produce an output block. This output block is then XORed with the plaintext block to produce the ciphertext. The encrypted output block is fed back into the AES encryption function to generate the next keystream block. This iterative process continues for all blocks of plaintext, allowing secure transformation without directly encrypting the plaintext multiple times.
Decryption Process
Decryption mirrors encryption in AES-256-OFB mode. The same key and IV are used to regenerate the keystream in the exact sequence as during encryption. Each keystream block is XORed with the corresponding ciphertext block to recover the original plaintext. Because the operations are identical for encryption and decryption, no separate decryption function is required beyond the XOR operation with the keystream.
Security Considerations
AES-256-OFB provides strong confidentiality when implemented correctly. The security relies on the randomness of the IV and the secrecy of the key. Reusing an IV with the same key compromises security, as it allows attackers to derive relationships between ciphertexts. Additionally, AES-256-OFB is resistant to padding oracle attacks since it operates in a stream cipher mode and does not require padding of plaintext blocks.
Applications
This mode of AES is suitable for encrypting data streams and scenarios where error propagation must be minimized. Since the encryption and decryption processes are identical and block errors do not affect subsequent blocks, AES-256-OFB is used in secure communications, file encryption, and network protocols requiring continuous data protection.