A symmetric encryption and decryption tool based on the CAST-128 algorithm. Supports text and Base64 encoding conversion to ensure secure data transmission.
CAST-128 (CAST5) used in PGP and GPG
Enter content and click Encrypt/Decrypt button
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When you need to transmit sensitive text over an unsecured network, the CAST encryption and decryption tool protects your data through a shared key mechanism. This tool uses the standard CAST-128 (CAST5) symmetric algorithm to convert plaintext into Base64 ciphertext. It supports variable key lengths from 40 to 128 bits, processes data in 64-bit blocks, and ensures security through 12 to 16 rounds of Feistel network iterations.
Why does the text look like gibberish after CAST encryption?
The ciphertext is output in Base64 format by default. You must maintain consistent encoding during encryption and decryption. Displaying raw binary data directly will result in garbled text.
What is the security difference between 40-bit and 128-bit keys?
A 128-bit key requires 2^128 operations to brute-force, whereas a 40-bit key only requires operations in the trillions. It is recommended to use keys longer than 12 bytes for sensitive data.
Losing your key will make the data permanently unrecoverable. Keys exceeding 16 bytes will be truncated. For non-ASCII characters, it is recommended to explicitly specify UTF-8 encoding.
Typical use cases: PGP email encryption (CAST5-IDEA combination) and legacy OpenSSL communication (CAST5-CBC mode). Example: Encrypting "你好" with the key "secure123" outputs "L3HjqPwT2GQ=". The exact same key is required to decrypt it back to the original text.
