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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) algorithm, used in PGP and GPG.
Please enter content and click Encrypt/Decrypt.
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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 64-bit data blocks per group, 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 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. We recommend using a key of 12 bytes or more for sensitive data.
Losing your key will make your data permanently unrecoverable. Keys exceeding 16 bytes will be truncated. For non-ASCII characters, we recommend explicitly specifying UTF-8 encoding.
Typical use cases: PGP email encryption (CAST5-IDEA combination) and legacy OpenSSL communication (CAST5-CBC mode). Example: Encrypting "Hello" with the key "secure123" outputs "L3HjqPwT2GQ="; the exact same key is required to decrypt it back to the original text.