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Checksum - School Project

ng flag

I'm working on a challenge at school on Internet, to learn programming and all security issue: "An api request is protected by checksum" and we have to bypass this. The checksum format is really weird; I've never something like it before. I think it convert all the string in an array of bytes, after that I don't know.

I search the algorithm to calculate the checksum.

Input : "a" --> "868969713355645187"
Input : "b" --> "208175330546845762"
Input : "example" --> "15743641371246298"
Input : "example1234" --> "1019540279168570200"
Input : "example1234778293782" --> "201687914436075516"

Length is 18-19 characters, only decimal

fgrieu avatar
ng flag
In general, such questions consisting mostly of ciphertext are off-[topic](https://crypto.stackexchange.com/help/on-topic) (see _Can I get data analysed here?_). [Possibly related Q](https://crypto.stackexchange.com/q/32704/555) with a general technique. I suggest to rewrite the question asking what techniques to use in such case, and giving a link to a [pastebin](https://pastebin.com/) or similar with more data, like 1-character messages for `0-9a-zA-z`. Also check if twice the same message yields twice the same code.
Neetoo InfoSec avatar
ng flag
I will do that ! Thanks
SAI Peregrinus avatar
si flag
Requests for analyzing ciphertext only (or similar) without a description of the system are off-topic here. Do you have any other info about the problem? You mention it's online, is it something where you are supposed to look at the JS and reverse-engineer it (in which case this belongs on reverse-engineering SE, not here)?
mangohost

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