# how can identify which cryptanalysis is used ( Indistinguishability cryptanalysis against classical ciphers) [duplicate]

I have 10 ciphertexts and 10 plain texts I want to know which cipher is from which plain text

how can I know this

I know the name of substitution cipher, transposition cipher, Vigen$$`$$ere cipher and case-insensitive letters-only one-time pad that are used in these 10 cipher and plain text

• Does this answer your question? How to determine which type of transposition cipher I have? Apr 23 at 22:27
• Here i have this ciphr "ODND O I TNTE GOLLIAA T S CHRHEAUEFE FNDIROCNTCT AUY USF OOZULAPES ZXEE EMECYLIDG IN ERDC IANALEELBVY" " and i have 10 files of plain text how can i decrypt i don't know ecxat which cryptanalysis is use Apr 23 at 23:06

## 1 Answer

Do frequency analysis by counting the number of occurrences of each letter.

For a transposition cipher, the counts will be similar to the underlying language (e.g. E T A O N will be common in English).

For a substitution cipher there will be the same distribution of counts as the underlying language, but the high counts will match with the wrong letters.

For Vigenere, the counts will be more uniform and closer to being equal.

If you have matching plaintext, the counts for transposition will be identical; the counts for substitution will be the same numbers in a different order; the counts for Vigenere will be very different.