Editing Triple DES (section)

==Security==
In general, Triple DES with three independent keys ([[#Keying options|keying option]]&nbsp;1) has a key length of 168&nbsp;bits (three 56-bit DES keys), but due to the [[meet-in-the-middle attack]], the effective security it provides is only 112&nbsp;bits.<ref name="NIST57r4" /> Keying option&nbsp;2 reduces the effective key size to 112&nbsp;bits (because the third key is the same as the first). However, this option is susceptible to certain [[chosen-plaintext]] or [[known-plaintext]] attacks,<ref>{{cite journal | author-link1 = Ralph Merkle | first = Ralph | last1 = Merkle | author-link2 = Martin Hellman | first2 = Martin | last2 = Hellman | url = http://cs.jhu.edu/~sdoshi/crypto/papers/p465-merkle.pdf | title = On the Security of Multiple Encryption | journal = [[Communications of the ACM]] | volume = 24 | issue = 7 | pages = 465–467 | date = July 1981 | doi = 10.1145/358699.358718 | citeseerx = 10.1.1.164.251 | s2cid = 11583508 | access-date = 2013-11-15 | archive-date = 2013-02-10 | archive-url = https://web.archive.org/web/20130210011347/http://cs.jhu.edu/~sdoshi/crypto/papers/p465-merkle.pdf | url-status = dead }}</ref><ref>{{cite conference | author-link1 = Paul van Oorschot | first1 = Paul | last1 = van Oorschot | author-link2 = Michael J. Wiener | first2 = Michael J. | last2 = Wiener | citeseerx = 10.1.1.66.6575 | title = A known-plaintext attack on two-key triple encryption | conference = [[EUROCRYPT]]'90, LNCS 473 | year = 1990 | pages = 318–325 }}</ref> and thus it is designated by NIST to have only 80&nbsp;[[bits of security]].<ref name="NIST57r4" /> This can be considered insecure; as a consequence, Triple DES's planned deprecation was announced by NIST in 2017.<ref name="tdea-deprecation">{{cite web |title=Update to Current Use and Deprecation of TDEA |url=https://csrc.nist.gov/News/2017/Update-to-Current-Use-and-Deprecation-of-TDEA |website=nist.gov |date=11 July 2017 |access-date=2 August 2019}}</ref>

[[Image:Sweet32.svg|thumb|right|Logo of the Sweet32 attack]]

The short block size of 64&nbsp;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.<ref>{{Cite web
| url=https://sweet32.info/
| title=Sweet32: Birthday attacks on 64-bit block ciphers in TLS and OpenVPN
| website=sweet32.info
| access-date=2017-09-05}}</ref> Practical Sweet32 attack on 3DES-based cipher-suites in TLS required <math>2^{36.6}</math> blocks (785&nbsp;GB) for a full attack, but researchers were lucky to get a collision just after around <math>2^{20}</math> blocks, which took only 25&nbsp;minutes.

{{Blockquote
|text=The security of TDEA is affected by the number of blocks processed with one key bundle. One key bundle shall not be used to apply cryptographic protection (e.g., encrypt) more than <math>2^{20}</math> 64-bit data blocks.
|sign=
|source=Recommendation for Triple Data Encryption Algorithm (TDEA) Block Cipher (SP 800-67 Rev2)<ref name="NIST67r2" />}}

[[OpenSSL]] does not include 3DES by default since version 1.1.0 (August 2016) and considers it a "weak cipher".<ref>{{cite web
| url=https://openssl-library.org/post/2016-08-25-sweet32/
| title=The SWEET32 Issue, CVE-2016-2183
| first=Rich
| last=Salz
| date=2016-08-24
| publisher=[[OpenSSL]]
| access-date=2024-10-11}}</ref>