Editing 7z (section)

=== Encryption ===
The 7z format supports [[encryption]] with the [[Advanced Encryption Standard|AES]] algorithm with a 256-bit key.  The key is generated from a user-supplied [[passphrase]] using an algorithm based on the [[SHA-256]] hash function. The SHA-256 is executed 2<sup>19</sup> (524288) times,<ref>{{Cite web |url=https://sourceforge.net/projects/sevenzip/?source=directory |title=7-zip source code |access-date=23 March 2018 |archive-date=22 March 2019 |archive-url=https://web.archive.org/web/20190322095659/https://sourceforge.net/projects/sevenzip/?source=directory |url-status=live }}</ref> which causes a significant delay on slow PCs before compression or extraction starts. This technique is called [[key stretching]] and is used to make a [[brute-force search]] for the passphrase more difficult.  Current GPU-based, and custom hardware attacks limit the effectiveness of this particular method of key stretching,<ref name="percival2009">[[Colin Percival]].
[http://www.tarsnap.com/scrypt.html scrypt] {{Webarchive|url=https://web.archive.org/web/20190528073159/https://www.tarsnap.com/scrypt.html |date=28 May 2019 }}.
As presented in
[http://www.tarsnap.com/scrypt/scrypt.pdf "Stronger Key Derivation via Sequential Memory-Hard Functions"] {{Webarchive|url=https://web.archive.org/web/20190414144147/http://www.tarsnap.com/scrypt/scrypt.pdf |date=14 April 2019 }}.
presented at BSDCan'09, May 2009.</ref> so it is still important to choose a strong password.
The 7z format provides the option to encrypt the filenames of a 7z archive.