The conceptually simple cipher of treating a message as a long number in one base and converting it to a different base does not appear among the historical elementary ciphers (substitution cipher, transposition cipher). Presumably it is because, using naive algorithms, radix conversion requires work quadratic in the length if the message (though it can be improved with divide and conquer). What sort of cryptanalytic techniques would work on it?
Change from base 37 (letters numbers space) to base 10, apply transposition cipher, change to base 26. Are certain pairs of bases more secure? I'm guessing relatively prime. Obviously converting from say base 100 to base 10 offers no security.
Was it ever tried as an early electro-mechanical cipher?
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