Noun
keystring (plural keystrings)
(computing) Any string of characters that has key (high) importance, such as a keyword or a keyphrase, but not necessarily a word in all senses of that term (as for example a phone number, an alphanumeric or numeric sequence, or string of symbols).
In Myszkowski transposition, recurrent keyword letters are numbered identically, TOMATO yielding a keystring of "532154." Source: Internet
In usual practice, subsequent occurrences of a keyword letter are treated as if the next letter in alphabetical order, e.g., the keyword TOMATO yields a numeric keystring of "532164." Source: Internet