Index of coincidence

1 · John Cook · Aug. 14, 2021, 6:47 p.m.
Index of coincidence is a statistic developed by William Freedman for use in cryptanalysis. It measures how unevenly symbols are distributed in a message. It’s a kind of signature that could be used, for example, to infer the language of a text, even if the text has been encrypted with a simple substitution cipher. It […] The post Index of coincidence first appeared on John D. Cook....