AES-128-CBC-CTS 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-WRAP

The AES-128-CBC-CTS algorithm combines the AES block cipher with Cipher Block Chaining (CBC) mode and Cipher Text Stealing (CTS) to provide secure encryption for data of arbitrary length. AES-128 uses a fixed key size of 128 bits, supporting 10 rounds of transformation, each consisting of SubBytes, ShiftRows, MixColumns, and AddRoundKey operations. This ensures a high level of diffusion and nonlinearity in the encrypted output.

Encryption Process

The encryption begins with the generation of a 128-bit key, which is expanded into a key schedule to be applied during each round. Plaintext is divided into 16-byte blocks. In CBC mode, each plaintext block is XORed with the previous ciphertext block before encryption. For the first block, an initialization vector (IV) is applied. CBC provides inter-block dependency, enhancing security by ensuring identical plaintext blocks produce different ciphertext when using a unique IV.

When the plaintext length is not a multiple of the block size, CTS is applied. CTS allows the last two blocks to be encrypted without padding, stealing the required bytes from the penultimate ciphertext block to complete the final ciphertext block. This preserves the original message length while maintaining strong security properties.

Decryption Process

Decryption reverses the steps of encryption. The last ciphertext blocks are processed with CTS logic to recover the original final block. Then, each block is decrypted using AES-128 and XORed with the preceding ciphertext block to restore the plaintext. The IV is used in the first block to reverse the CBC chaining. CTS ensures exact reconstruction of plaintext length without introducing padding artifacts.

Security Considerations

AES-128-CBC-CTS provides confidentiality through strong AES encryption, block chaining, and proper handling of non-block-aligned data. The key must remain secret, and IVs should be unique and unpredictable for each encryption operation. Using this combination prevents certain attacks associated with standard CBC when plaintext lengths are not multiples of the block size.

Applications

This algorithm is widely used in secure data storage, file encryption, and communication protocols where fixed-length block ciphers need to handle variable-length input efficiently. CTS allows direct encryption of arbitrary-length messages without padding, simplifying implementation and avoiding padding-related vulnerabilities.

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