Most well-known symmetric ciphers are block ciphers. The plaintext to be encrypted must be split into fixed-length blocks (usually 64 or 128 bits long) and fed to the cipher one at a time. The resulting blocks (of the same length) are . . .
Most well-known symmetric ciphers are block ciphers. The plaintext to be encrypted must be split into fixed-length blocks (usually 64 or 128 bits long) and fed to the cipher one at a time. The resulting blocks (of the same length) are concatenated to form the ciphertext.

The ciphers in widespread use today vary in strength, key length, block size and their approach to encrypting data. Some of the popular ciphers (IDEA, Twofish, Rijndael) are implemented by eponymous modules in the Crypt:: namespace on the CPAN (Crypt::IDEA and so on).

To decide which cipher to use for a particular application, one must consider the strength and speed required, and the computational resources available. The decision cannot be made without research, but IDEA is often considered the best practical choice for a general purpose cipher.

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