Nothing-up-my-sleeve number
Cryptography number with no hidden properties
Summary
In cryptography, nothing-up-my-sleeve numbers are any numbers which, by their construction, are above suspicion of hidden properties. They are used in creating cryptographic functions such as hashes and ciphers. These algorithms often need randomized constants for mixing or initialization purposes. The cryptographer may wish to pick these values in a way that demonstrates the constants were not selected for a nefarious purpose, for example, to create a backdoor to the algorithm. These fears can be allayed by using numbers created in a way that leaves little room for adjustment. An example would be the use of initial digits from the number π as the constants. Using digits of π millions of places after the decimal point would not be considered trustworthy because the algorithm designer might have selected that starting point because it created a secret weakness the designer could later exploit—though even with natural-seeming selections, enough entropy exists in the possible choices that the utility of these numbers has been questioned.
Originally created by ArnoldReinhold
12/6/2004, 3:35:25 PM
Modified
6/4/2026, 9:22:02 PM
Recent revisions
/* Limitations */ grammar
Grammar.
Some ce. Probably needs more.
/* Counterexamples */ | Altered template type. Add: isbn, chapter-url, pages, volume, series, chapter, title. Removed or converted URL. Normalized parameter names. | [[:en:WP:UCB|Use this tool]]. [[:en:WP:DBUG|Report bugs]]. | #UCB_Gadget
Fix apparent typo 'SaveCurves'
/* Manipulatable, but not trivially */ new
The page citation in the footnote was not correct when I referred to my 2nd edition of the book. After reading the DES chapter, I found the actual discussion on page 289 and thus I cited the sentence.
/* Examples */ improve potentially misleading info
Added date. | [[:en:WP:UCB|Use this bot]]. [[:en:WP:DBUG|Report bugs]]. | Suggested by Abductive | [[Category:Cryptography]] | #UCB_Category 25/220
improve formatting
Undid revision [[Special:Diff/1274269314|1274269314]] by [[Special:Contributions/Beland|Beland]] ([[User talk:Beland|talk]]) - The golden ratio is almost always written using lowercase phi. Therefore, a capital phi ''would'' be a typo
convert special characters found by [[Wikipedia:Typo Team/moss]] (via [[WP:JWB]])
Changing [[Wikipedia:Short description|short description]] from "Numbers used by cryptographers to show that they are working in good faith" to "Cryptography number with no hidden properties"
/* Examples */ fixed link
Fix citation
Add source for Salsa20 ASCII constants
/* Counterexamples */
Add MD2
/* Examples */ "without the initial 3" shorter
