Editing SHA-1 (section)

== Implementations ==
Below is a list of cryptography libraries that support SHA-1:

* [[Botan (programming library)|Botan]]
* [[Bouncy Castle (cryptography)|Bouncy Castle]]
* [[cryptlib]]
* [[Crypto++]]
* [[Libgcrypt]]
* [[Mbed TLS]]
* [[Nettle (cryptographic library)|Nettle]]
* [[LibreSSL]]
* [[OpenSSL]]
* [[GnuTLS]]

Hardware acceleration is provided by the following processor extensions:

* [[Intel SHA extensions]]: Available on some Intel and AMD x86 processors.
* [[VIA PadLock]]
* IBM [[z/Architecture]]:  Available since 2003 as part of the Message-Security-Assist Extension<ref>IBM z/Architecture Principles of Operation, publication number SA22-7832.  See KIMD and KLMD instructions in Chapter 7.</ref>

=== Collision countermeasure ===
In the wake of SHAttered, Marc Stevens and Dan Shumow published "sha1collisiondetection" (SHA-1CD), a variant of SHA-1 that detects collision attacks and changes the hash output when one is detected. The false positive rate is 2<sup>−90</sup>.<ref>{{cite web |last1=Stevens |first1=Marc |title=cr-marcstevens/sha1collisiondetection:  Library and command line tool to detect SHA-1 collision in a file  |url=https://github.com/cr-marcstevens/sha1collisiondetection |date=2017}}</ref> SHA-1CD is used by [[GitHub]] since March 2017 and [[git]] since version 2.13.0 of May 2017.<ref>{{cite web |last1=King |first1=Jeff |title=Git 2.13 has been released |url=https://github.blog/2017-05-10-git-2-13-has-been-released/ |website=The GitHub Blog |date=10 May 2017}}</ref>