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 Mar3 comment How to solve the reverse of an equation that uses MOD? @Mok-KongShen so what you're saying is the solution is y=(62135*x) mod 380951. From initial testing I think this is the correct solution. Thanks! Mar3 revised How to solve the reverse of an equation that uses MOD? added 2 characters in body Mar3 awarded Editor Mar3 revised How to solve the reverse of an equation that uses MOD? Simpler valid answer in the example Mar3 comment How to solve the reverse of an equation that uses MOD? Incidentally through experimentation I have determined that 83172+380951*2438=928841710 then 928841710/3182=291905 then 291905 mod 380951 is 291905 so I suspect if I could somehow calculate the 2834 versus exhaustively searching for it then that could be workable solution. Mar3 comment How to solve the reverse of an equation that uses MOD? Ok, so I implemented the modular exponentiation function using the right to left binary method. 3182^380949 mod 380951=200354 so 200354*83172 mod 380951 = 284246 not the 1434758 I was expecting. Any ideas where I've gone wrong? Mar2 comment How to solve the reverse of an equation that uses MOD? Sadly I don't even have a method of calculating a number as large as 3182^(380951-2). I'm hoping to find a method shorter than calculating the approx 3000 possible multipliers. Mar1 asked How to solve the reverse of an equation that uses MOD? Feb3 comment What is the key strength reduction encrypting only 160 bits of data using RSA1024 for signatures? Given that the public key and modulus are stored in a hardware device, it is sent some data and a signature. It uses the keys to decrypt the signature and compare it against a locally calculated cryptographic hash. I just happen to know that once decrypted the signature is a 160 bit hash preceeded by 0x1f 0xfffff....fff (864 bits of padding). I was hoping this could somehow be used to find a way to generate my own signature blocks that would correctly decrypt and validate. Feb3 awarded Student Feb3 awarded Scholar Feb3 accepted What is the key strength reduction encrypting only 160 bits of data using RSA1024 for signatures? Feb3 comment What is the key strength reduction encrypting only 160 bits of data using RSA1024 for signatures? I understood that introducing random data in the block to be RSA encrypted was necessary. So based on your answer, padding the cryptographic hash even with 0xff does not introduce any weaknesses into the system? Feb3 asked What is the key strength reduction encrypting only 160 bits of data using RSA1024 for signatures?