Serpent Encryption & Decryption Tool

Encrypt or decrypt text with Serpent

Serpent is a symmetric block cipher: the same secret key is used to encrypt and later decrypt data. This page applies Serpent to text and lets you set a key size, operation mode, and padding. The available key sizes are 128, 192, and 256 bits; the modes are ECB and CBC; the padding choices are PKCS7 and zero padding. CBC requires an initialization vector (IV), while ECB does not.

The cipher processes fixed-size blocks, so text that does not fill a block needs a padding convention. PKCS7 records how many padding bytes were added; zero padding appends zero bytes and can be ambiguous if the original text itself ends with zero bytes. In CBC mode, the IV affects the first block and must be available to decrypt the same ciphertext. The output can be copied as hexadecimal or Base64 text.

NIST’s AES selection history lists Serpent among five finalists considered in the AES process. That historical selection does not mean this page’s configuration is an approved or recommended way to protect current sensitive data. A cipher alone does not provide authenticated encryption or a complete key-management workflow.

Match the settings on both sides

1. Choose encrypt or decrypt

   For encryption, enter readable text. For decryption, provide ciphertext in the supported hexadecimal or Base64 input format.

2. Set the key and cipher options

   Select 128, 192, or 256 bits and enter a key that matches the selected length. Choose ECB or CBC and the padding convention. CBC encryption generates an IV by default; retain the displayed IV and supply the same value, mode, key, and padding when decrypting.

3. Process and preserve the output format

   Run the operation and copy either the hexadecimal or Base64 output. These are encodings of bytes, not separate encryption methods. When decrypting, select the matching ciphertext encoding and use exactly the settings used to encrypt.

A simple round-trip check is to encrypt a short test phrase, then decrypt the result with the same key, mode, padding, and (for CBC) IV. The recovered text should match the original input.

Key, IV, and output questions

Do not treat a cipher page as a secure vault

Use non-sensitive examples for learning or compatibility checks. Do not enter passwords, private records, credentials, or confidential business data unless you have independently verified the page’s data handling and your organization permits that use.

• ECB reveals patterns when repeated plaintext blocks produce repeated ciphertext blocks. CBC requires a correctly generated and preserved IV, and neither mode by itself authenticates that data was not changed.
• This page does not establish a complete security protocol, authenticate messages, manage keys, or certify that an implementation is suitable for production. For new systems, use established cryptographic libraries and reviewed authenticated-encryption designs.
• Keep the key and IV with care; anyone with the required key and parameters can decrypt the ciphertext.