Editing Zeroisation (section)

==Software==
In modern [[software]] based cryptographic modules, zeroisation is made considerably more complex by issues such as [[virtual memory]], [[compiler]] [[optimization (computer science)|optimisation]]s<ref>{{cite web|url=https://buildsecurityin.us-cert.gov/bsi/articles/knowledge/coding/771-BSI.html |title=MEMSET |access-date=March 21, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130221133145/https://buildsecurityin.us-cert.gov/bsi/articles/knowledge/coding/771-BSI.html |archive-date=February 21, 2013 }}</ref> and use of [[flash memory]].<ref>{{cite web|url=http://cio.nist.gov/esd/emaildir/lists/cc-cmt/msg01706.html |title=Archived copy |access-date=March 21, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130307044459/http://cio.nist.gov/esd/emaildir/lists/cc-cmt/msg01706.html |archive-date=March 7, 2013 }}</ref> Also, zeroisation may need to be applied not only to the key, but also to a [[plaintext]] and some intermediate values. A cryptographic software developer must have an intimate understanding of [[memory management]] in a machine, and be prepared to zeroise data whenever a sensitive device might move outside the security boundary. Typically this will involve overwriting the data with zeroes, but in the case of some types of [[non-volatile storage]] the process is much more complex; see ''[[data remanence]]''.

As well as zeroising data due to memory management, software designers consider performing zeroisation:
* When an application changes mode (e.g. to a test mode) or user;
* When a [[computer process]] changes [[computer security|privileges]];
* On termination (including abnormal termination);
* On any error condition which may indicate instability or tampering;
* Upon user request;
* Immediately, the last time the parameter is required; and
* Possibly if a parameter has not been required for some time.
Informally, software developers may also use '''zeroise''' to mean any overwriting of sensitive data, not necessarily of a cryptographic nature.