# Triple DES

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In cryptography, Triple DES (3DES[1]) is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) block cipher, which applies the Data Encryption Standard (DES) cipher algorithm three times to each data block. Because of the availability of increasing computational power, the key size of the original DES cipher was becoming subject to brute force attacks; Triple DES was designed to provide a relatively simple method of increasing the key size of DES to protect against such attacks, without designing a completely new block cipher algorithm.

## Contents

### Definitive standards

The Triple Data Encryption Algorithm (TDEA) is defined in each of:

### Name of the algorithm

The earliest standard that defines the algorithm (ANS X9.52, published in 1998) describes it as the "Triple Data Encryption Algorithm (TDEA)" — i.e. three operations of the Data Encryption Algorithm specified in ANSI X3.92 — and does not use the terms "Triple DES" or "DES" at all. FIPS PUB 46-3 (1999) defines the "Triple Data Encryption Algorithm (TDEA)", but also uses the terms "DES" and "Triple DES". It uses the terms "Data Encryption Algorithm" and "DES" interchangeably, including starting the specification with:

The Data Encryption Standard (DES) shall consist of the following Data Encryption Algorithm (DES) [sic] and Triple Data Encryption Algorithm (TDEA, as described in ANSI X9.52).

NIST SP 800-67 (2004, 2008[5]) primarily uses the term TDEA, but also refers to "Triple DES (TDEA)". ISO/IEC 18033-3 (2005) uses "TDEA", but mentions that: