In
cryptography
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...
, Triple DES (3DES or TDES), officially the Triple Data Encryption Algorithm (TDEA or Triple DEA), is a
symmetric-key block cipher
In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called ''blocks''. Block ciphers are specified cryptographic primitive, elementary components in the design of many cryptographic protocols and ...
, which applies the
DES
Des is a masculine given name, mostly a short form (hypocorism) of Desmond. People named Des include:
People
* Des Buckingham, English football manager
* Des Corcoran, (1928–2004), Australian politician
* Des Dillon (disambiguation), sever ...
cipher algorithm three times to each data block. The Data Encryption Standard's (DES) 56-bit key is no longer considered adequate in the face of modern cryptanalytic techniques and supercomputing power. A
CVE released in 2016,
CVE-2016-2183' disclosed a major security vulnerability in DES and 3DES encryption algorithms. This CVE, combined with the inadequate key size of DES and 3DES,
NIST
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...
has deprecated DES and 3DES for ''new'' applications in 2017, and for ''all'' applications by the end of 2023. It has been replaced with the more secure, more robust
AES.
While the government and industry standards abbreviate the algorithm's name as TDES (Triple DES) and TDEA (Triple Data Encryption Algorithm), RFC 1851 referred to it as 3DES from the time it first promulgated the idea, and this namesake has since come into wide use by most vendors, users, and cryptographers.
History
In 1978, a triple encryption method using DES with two 56-bit keys was proposed by Walter Tuchman; in 1981 Merkle and Hellman proposed a more secure triple key version of 3DES with 112 bits of security.
Standards
The Triple Data Encryption Algorithm is variously defined in several standards documents:
*
RFC
RFC may refer to:
Computing
* Request for Comments, a memorandum on Internet standards
* Request for change, change management
* Remote Function Call, in SAP computer systems
* Rhye's and Fall of Civilization, a modification for Sid Meier's Civ ...
1851, ''The ESP Triple DES Transform'' (approved in 1995)
*
ANSI
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
ANS X9.52-1998 ''Triple Data Encryption Algorithm Modes of Operation''
[ Extends ANSI X3.92-1981 ''Data Encryption Algorithm''.] (approved in 1998, withdrawn in 2008)
*
FIPS PUB 46-3 ''Data Encryption Standard (DES)'' (approved in 1999, withdrawn in 2005)
*
NIST
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...
Special Publication 800-67 Revision 2 ''Recommendation for the Triple Data Encryption Algorithm (TDEA) Block Cipher''
(approved in 2017)
*
ISO
ISO is the most common abbreviation for the International Organization for Standardization.
ISO or Iso may also refer to: Business and finance
* Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007
* Iso ...
/
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
18033-3:2010: Part 3: Block ciphers (approved in 2005)
Algorithm
The original DES cipher's
key size
In cryptography, key size, key length, or key space refer to the number of bits in a key used by a cryptographic algorithm (such as a cipher).
Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest ...
of 56 bits was generally sufficient when that algorithm was designed, but the availability of increasing computational power made
brute-force attack
In cryptography, a brute-force attack consists of an attacker submitting many passwords or passphrases with the hope of eventually guessing correctly. The attacker systematically checks all possible passwords and passphrases until the correct ...
s feasible. Triple DES provides a relatively simple method of increasing the key size of DES to protect against such attacks, without the need to design a completely new block cipher algorithm.
A naive approach to increase strength of a block encryption algorithm with short key length (like DES) would be to use two keys
instead of one, and encrypt each block twice:
. If the original key length is
bits, one would hope this scheme provides security equivalent to using key
bits long. Unfortunately, this approach is vulnerable to
meet-in-the-middle attack: given a
known plaintext
The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secre ...
pair
, such that
, one can recover the key pair
in
steps, instead of the
steps one would expect from an ideally secure algorithm with
bits of key.
Therefore, Triple DES uses a "key bundle" that comprises three DES
keys,
,
and
, each of 56 bits (excluding
parity bit
A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes) ...
s). The encryption algorithm is:
:
That is, DES encrypt with
, DES ''decrypt'' with
, then DES encrypt with
.
Decryption is the reverse:
:
That is, decrypt with
, ''encrypt'' with
, then decrypt with
.
Each triple encryption encrypts
one block of 64 bits of data.
In each case the middle operation is the reverse of the first and last. This improves the strength of the algorithm when using
keying option 2 and provides
backward compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
with DES with keying option 3.
Keying options
The standards define three keying options:
; Keying option 1
: All three keys are independent. Sometimes known as 3TDEA
or triple-length keys.
: This is the strongest, with 3 × 56 = 168 independent key bits. It is still vulnerable to
meet-in-the-middle attack, but the attack requires 2
2 × 56 steps.
; Keying option 2
: K
1 and K
2 are independent, and K
3 = K
1. Sometimes known as 2TDEA
or double-length keys.
[
: This provides a shorter key length of 112 bits and a reasonable compromise between DES and Keying option 1, with the same caveat as above. This is an improvement over "double DES" which only requires 256 steps to attack. NIST has deprecated this option.]
; Keying option 3
: All three keys are identical, i.e. K1 = K2 = K3.
: This is backward compatible with DES, since two operations cancel out. ISO/IEC 18033-3 never allowed this option, and NIST no longer allows K1 = K2 or K2 = K3.
Each DES key is 8 odd-parity bytes, with 56 bits of key and 8 bits of error-detection. A key bundle requires 24 bytes for option 1, 16 for option 2, or 8 for option 3.
NIST (and the current TCG specifications version 2.0 of approved algorithms for Trusted Platform Module
Trusted Platform Module (TPM, also known as ISO/IEC 11889) is an international standard for a secure cryptoprocessor, a dedicated microcontroller designed to secure hardware through integrated cryptographic keys. The term can also refer to a ch ...
) also disallows using any one of the 64 following 64-bit values in any keys (note that 32 of them are the binary complement of the 32 others; and that 32 of these keys are also the reverse permutation of bytes of the 32 others), listed here in hexadecimal (in each byte, the least significant bit is an odd-parity generated bit, it is discarded when forming the effective 56-bit keys):
01.01.01.01.01.01.01.01, FE.FE.FE.FE.FE.FE.FE.FE, E0.FE.FE.E0.F1.FE.FE.F1, 1F.01.01.1F.0E.01.01.0E,
01.01.FE.FE.01.01.FE.FE, FE.FE.01.01.FE.FE.01.01, E0.FE.01.1F.F1.FE.01.0E, 1F.01.FE.E0.0E.01.FE.F1,
01.01.E0.E0.01.01.F1.F1, FE.FE.1F.1F.FE.FE.0E.0E, E0.FE.1F.01.F1.FE.0E.01, 1F.01.E0.FE.0E.01.F1.FE,
01.01.1F.1F.01.01.0E.0E, FE.FE.E0.E0.FE.FE.F1.F1, E0.FE.E0.FE.F1.FE.F1.FE, 1F.01.1F.01.0E.01.0E.01,
01.FE.01.FE.01.FE.01.FE, FE.01.FE.01.FE.01.FE.01, E0.01.FE.1F.F1.01.FE.0E, 1F.FE.01.E0.0E.FE.01.F1,
01.FE.FE.01.01.FE.FE.01, FE.01.01.FE.FE.01.01.FE, E0.01.01.E0.F1.01.01.F1, 1F.FE.FE.1F.0E.FE.FE.0E,
01.FE.E0.1F.01.FE.F1.0E, FE.01.1F.E0.FE.01.0E.F1, E0.01.1F.FE.F1.01.0E.FE, 1F.FE.E0.01.0E.FE.F1.01,
01.FE.1F.E0.01.FE.0E.F1, FE.01.E0.1F.FE.01.F1.0E, E0.01.E0.01.F1.01.F1.01, 1F.FE.1F.FE.0E.FE.0E.FE,
01.E0.01.E0.01.F1.01.F1, FE.1F.FE.1F.FE.0E.FE.0E, E0.1F.FE.01.F1.0E.FE.01, 1F.E0.01.FE.0E.F1.01.FE,
01.E0.FE.1F.01.F1.FE.0E, FE.1F.01.E0.FE.0E.01.F1, E0.1F.01.FE.F1.0E.01.FE, 1F.E0.FE.01.0E.F1.FE.01,
01.E0.E0.01.01.F1.F1.01, FE.1F.1F.FE.FE.0E.0E.FE, E0.1F.1F.E0.F1.0E.0E.F1, 1F.E0.E0.1F.0E.F1.F1.0E,
01.E0.1F.FE.01.F1.0E.FE, FE.1F.E0.01.FE.0E.F1.01, E0.1F.E0.1F.F1.0E.F1.0E, 1F.E0.1F.E0.0E.F1.0E.F1,
01.1F.01.1F.01.0E.01.0E, FE.E0.FE.E0.FE.F1.FE.F1, E0.E0.FE.FE.F1.F1.FE.FE, 1F.1F.01.01.0E.0E.01.01,
01.1F.FE.E0.01.0E.FE.F1, FE.E0.01.1F.FE.F1.01.0E, E0.E0.01.01.F1.F1.01.01, 1F.1F.FE.FE.0E.0E.FE.FE,
01.1F.E0.FE.01.0E.F1.FE, FE.E0.1F.01.FE.F1.0E.01, E0.E0.1F.1F.F1.F1.0E.0E, 1F.1F.E0.E0.0E.0E.F1.F1,
01.1F.1F.01.01.0E.0E.01, FE.E0.E0.FE.FE.F1.F1.FE, E0.E0.E0.E0.F1.F1.F1.F1, 1F.1F.1F.1F.0E.0E.0E.0E,
With these restrictions on allowed keys, Triple DES has been reapproved with keying options 1 and 2 only. Generally the three keys are generated by taking 24 bytes from a strong random generator and only keying option 1 should be used (option 2 needs only 16 random bytes, but strong random generators are hard to assert and it's considered best practice to use only option 1).
Encryption of more than one block
As with all block ciphers, encryption and decryption of multiple blocks of data may be performed using a variety of modes of operation
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity.
A block cipher by itself is only suitable for the secure cryptographic transfor ...
, which can generally be defined independently of the block cipher algorithm. However, ANS X9.52 specifies directly, and NIST SP 800-67 specifies via SP 800-38A that some modes shall only be used with certain constraints on them that do not necessarily apply to general specifications of those modes. For example, ANS X9.52 specifies that for cipher block chaining
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity.
A block cipher by itself is only suitable for the secure cryptographic transforma ...
, the initialization vector
In cryptography, an initialization vector (IV) or starting variable (SV) is an input to a cryptographic primitive being used to provide the initial state. The IV is typically required to be random or pseudorandom, but sometimes an IV only needs to ...
shall be different each time, whereas ISO/IEC 10116 does not. FIPS PUB 46-3 and ISO/IEC 18033-3 define only the single block algorithm, and do not place any restrictions on the modes of operation for multiple blocks.
Security
In general, Triple DES with three independent keys ( keying option 1) has a key length of 168 bits (three 56-bit DES keys), but due to the meet-in-the-middle attack, the effective security it provides is only 112 bits. Keying option 2 reduces the effective key size to 112 bits (because the third key is the same as the first). However, this option is susceptible to certain chosen-plaintext or known-plaintext attacks, and thus it is designated by NIST to have only 80 bits of security
In cryptography, security level is a measure of the strength that a cryptographic primitive — such as a cipher or hash function — achieves. Security level is usually expressed as a number of "bits of security" (also security strengt ...
. This can be considered insecure, and, as consequence Triple DES has been deprecated by NIST in 2017.
The short block size of 64 bits makes 3DES vulnerable to block collision attacks if it is used to encrypt large amounts of data with the same key. The Sweet32 attack shows how this can be exploited in TLS and OpenVPN. Practical Sweet32 attack on 3DES-based cipher-suites in TLS required blocks (785 GB) for a full attack, but researchers were lucky to get a collision just after around blocks, which took only 25 minutes.
OpenSSL
OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping or need to identify the party at the other end. It is widely used by Internet servers, including the majority of HTT ...
does not include 3DES by default since version 1.1.0 (August 2016) and considers it a "weak cipher".
Usage
The electronic payment
An e-commerce payment system (or an electronic payment system) facilitates the acceptance of electronic payment for offline transfer, also known as a subcomponent of electronic data interchange (EDI), e-commerce payment systems have become incre ...
industry uses Triple DES and continues to develop and promulgate standards based upon it, such as EMV
EMV is a payment method based on a technical standard for smart payment cards and for payment terminals and automated teller machines which can accept them. EMV stands for " Europay, Mastercard, and Visa", the three companies that created th ...
.
Earlier versions of Microsoft OneNote
Microsoft OneNote is a note-taking software developed by Microsoft. It is available as part of the Microsoft Office suite and since 2014 has been free on all platforms outside the suite. OneNote is designed for free-form information gathering ...
, Microsoft Outlook
Microsoft Outlook is a personal information manager software system from Microsoft, available as a part of the Microsoft Office and Microsoft 365 software suites. Though primarily an email client, Outlook also includes such functions as Calen ...
2007 and Microsoft System Center Configuration Manager
Microsoft Endpoint Configuration Manager, formerly System Center Configuration Manager and Systems Management Server (SMS) is a systems management software product developed by Microsoft for managing large groups of computers providing remote cont ...
2012 use Triple DES to password-protect user content and system data. However, in December 2018, Microsoft announced the retirement of 3DES throughout their Office 365 service.
Firefox
Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current and ...
and Mozilla Thunderbird
Mozilla Thunderbird is a free and open-source cross-platform email client, personal information manager, news client, RSS and chat client developed by the Mozilla Foundation and operated by subsidiary MZLA Technologies Corporation. The project s ...
Mozilla NSS source code
Se
Explanation of directory structure
(especially the introductory and "security" sections) for background information. use Triple DES in
CBC mode
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity.
A block cipher by itself is only suitable for the secure cryptographic transfor ...
to encrypt website authentication login credentials when using a master password.
Implementations
Below is a list of cryptography libraries that support Triple DES:
*
Botan
*
Bouncy Castle
Bounce or The Bounce may refer to:
* Deflection (physics), the event where an object collides with and bounces against a plane surface
Books
* Mr. Bounce, a character from the Mr. Men series of children's books
Broadcasting, film and TV
* ''B ...
*
cryptlib
cryptlib is an open-source cross-platform software security toolkit library. It is distributed under the Sleepycat License, a free software license compatible with the GNU General Public License. Alternatively, cryptlib is available under a pr ...
*
Crypto++
Crypto++ (also known as CryptoPP, libcrypto++, and libcryptopp) is a free and open-source C++ class library of cryptographic algorithms and schemes written by Wei Dai. Crypto++ has been widely used in academia, student projects, open-source, and no ...
*
Libgcrypt
Libgcrypt is a cryptography library developed as a separated module of GnuPG.
It can also be used independently of GnuPG, but depends on its error-reporting library Libgpg-error.
It provides functions for all fundamental cryptographic building blo ...
*
Nettle
{{redirect, Nettle
Nettle refers to plants with stinging hairs, particularly those of the genus ''Urtica''. It can also refer to plants which resemble ''Urtica'' species in appearance but do not have stinging hairs. Plants called "nettle" include ...
*
OpenSSL
OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping or need to identify the party at the other end. It is widely used by Internet servers, including the majority of HTT ...
*
wolfSSL
wolfSSL is a small, portable, embedded SSL/TLS library targeted for use by embedded systems developers. It is an open source implementation of TLS (SSL 3.0, TLS 1.0, 1.1, 1.2, 1.3, and DTLS 1.0, 1.2, and 1.3) written in the C programming lan ...
*
Trusted Platform Module
Trusted Platform Module (TPM, also known as ISO/IEC 11889) is an international standard for a secure cryptoprocessor, a dedicated microcontroller designed to secure hardware through integrated cryptographic keys. The term can also refer to a ch ...
(alias TPM, hardware implementation)
Some implementations above may not include 3DES in the default build, in later or more recent versions.
See also
*
DES-X
*
Advanced Encryption Standard
The Advanced Encryption Standard (AES), also known by its original name Rijndael (), is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.
AES is a variant ...
(AES)
*
Feistel cipher
In cryptography, a Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel, who did pioneering research whi ...
*
Walter Tuchman
References and notes
{{Cryptography navbox , block
Broken block ciphers
Data Encryption Standard
de:Data Encryption Standard#Triple-DES