Networking / Beginners

Cipher Examples

Following are several examples of ciphers:

DEA (DES) A very long time ago, the National Institute of Standards and Technology (NIST) realized that sensitive data needed to be protected in a standardized way. The Data Encryption Standard (DES) was born, and this standard was implemented with the Data Encryption Algorithm (DEA).

Major parts of the inner workings of DEA were invented by the IBM corporation; it was originally known as the Lucifer cipher within IBM. NIST accepted, modified, and re-branded the Lucifer cipher.

DEA is a symmetric block cipher. This means that it works by performing a series of transpositions and substitutions on blocks of the plain-text. Its symmetric aspect means that it uses the same key for encryption and decryption. The key size used in DEA is 64 bits long.

Note IBM's original Lucifer cipher from which DEA was derived used 128-bit-long keys. For whatever reasons, NIST chose to downgrade the key length to 64 bits.

DES and its associated algorithm were in use for a long time in many applications, and eventually NIST deployed a newer and stronger algorithm. NIST determined that it was time to retire the older DEA partly because of the vastly increased computing capabilities of the then-current computer systems. In fact, the second shoe finally dropped when the efficacy of DES was compromised in 1998.

3DES (AES) NIST called for the development and submission for a newer, better, and stronger method of protecting sensitive information after it was decided that the aging DEA was no longer sufficient, and the Advanced Encryption Standard (AES) was born. AES was implemented with the 3DES (pronounced Triple-DES), also known as the Rijndael Algorithm, which is a play of the names of its two inventors, Joan Daemen and Vincent Rijmen.

Like its predecessor, 3DES is also a symmetric block cipher, but it supports larger block sizes than DES. Specifically, it supports plain-text block sizes of 128, 192, and 256 bits, as well as corresponding key lengths of 128, 192, and 256 bits for encryption. Generating cipher-text from plain-text using 3DES is generally a more computationally demanding process when compared to DES. This means that more powerful hardware is required when working with 3DES.

RC4 Rivest Cipher 4 (RC4), named after its inventor, Ron Rivest, is a popular and widely used cipher. It uses symmetric keys and is a stream cipher. The key size or length used in RC4 is variable but should be between 1 and 255 bytes.

Being a stream-based cipher, RC4 is quite fast in its execution and not too computationally demanding. Because it is stream-based, encryption and decryption operate on the individual bits (or bytes) of the plain-text.

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