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Algorithm, crypto help

By Monki_100 ·
Hey, people, I need help.

A friend of mine has a quite interesting- well, for some- algorithm. We often exchange codes, which the other person attempts to decrypt. The problem is, most of the time, codes are fine with me. Mathematical algorithms, not so much.

So he has four versions of the exact same text encoded with the exact same algorithm, and refuses to explain further.

My first question is how can you have the exact same text and exact same algorithm, but get:

1 N0kic5C7sJWLzl5xKC6oeYThhwVZ/M mvutJmlO5GQH07WVXyHhyWwuZfpcwM SJ4fBc9x6l40v5ObXLJFOdCSgw==

2 Q3sS+qXlHgGMlGA92UUBvK9741JEk8 SzNTzrjlkkJVNlQMEeCRO9FVLCa6bz Emr80170+QQa/vshxAzxAZteTw==

3 DkUoRooUkSPqJh7zt3E3MvVvcF5xTU nnACOm3gYKTpGfNXduT30twy/meiE+ qs28m3lIwcAE4p7Rgm0Sxc7fxA==

4 A8Q1vwCp7avl0yV6amGKlgL1fFbuCc gx7E07ppc91/U/usCzFG8UUGbc6pQ9 0pu2nSTQShJ+VMKaqoScT7McNg==

the == signs at the end of all of them just signal the end of that string.
So, I'm looking at this, and I realize I have no idea where to even start. Any hints you have would be welcome...or even just the solution

Thanks!

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Keys

by oldbaritone In reply to Algorithm, crypto help

Hello, do you understand what crypto is all about?

how can you have the exact same text and exact same algorithm, but get [different results]

OF COURSE you get different results - otherwise crypto would be pointless.

Depending on the algorithm, there is either one (if it's a "symmetrical" algorithm like DES) or two (if it's "asymmetrical" like PKI) keys for the encryption. If you use a different encryption key (think password, only longer) you will get a different encryption result.

With a symmetrical encryption (DES, for example) you simply input the encrypted string and key into the same function that created it. If it's asymmetrical, you use one algorithm and key for encryption, and a different algorithm and key for decryption.

For a first guess, I'd try DES. (Hope your friend isn't being too mean... currently, many use 3DES or triple-DES, which is simply re-encrypting the first encrypted result twice more using different keys - MUCH more difficult to crack, because the intermediate results are still encrypted and you can't use pattern matching on them)

There are several ways to recover the key, and since you have a sample of four different encryptions of the same text, it should be obvious when you get the key that you have the correct algorithm and keys.

Have fun.

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