Editing Key (cryptography) (section)

== Key generation ==
{{Main|Key generation}}
To prevent a key from being guessed, keys need to be generated randomly and contain sufficient [[Entropy (information theory)|entropy]]. The problem of how to safely generate random keys is difficult and has been addressed in many ways by various cryptographic systems. A key can directly be generated by using the output of a Random Bit Generator (RBG), a system that generates a sequence of unpredictable and unbiased bits.<ref>{{Cite web|last=Dang|first=Quynh|date=August 2012|title=Recommendation for Applications Using Approved Hash Algorithms|url=https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-107r1.pdf|access-date=2021-04-02}}</ref> A RBG can be used to directly produce either a symmetric key or the random output for an asymmetric key pair generation. Alternatively, a key can also be indirectly created during a key-agreement transaction, from another key or from a password.<ref name=NIST>{{cite journal |url=https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf | doi=10.6028/NIST.SP.800-132 | title=Recommendation for password-based key derivation | date=2010 | last1=Turan | first1=M. S. | last2=Barker | first2=E. B. | last3=Burr | first3=W. E. | last4=Chen | first4=L. | s2cid=56801929 }}</ref>

Some operating systems include tools for "collecting" entropy from the timing of unpredictable operations such as disk drive head movements. For the production of small amounts of keying material, ordinary dice provide a good source of high-quality randomness.