Hi leannonn,
usually it is not possible, unless you are talking about really simple cryptography algorithms, such as rotation-, simple-hash and XOR-ciphers. Otherwise, ciphered text should resemble, as much as possible, "white noise" (random text), and be also immune to frequency analysis.
Aleksandar BradarićSoftware DeveloperAuthor Commented:
Hi,
> unless you are talking about really simple cryptography algorithms, such as
> rotation-, simple-hash and XOR-ciphers
So, there is no way to identify any kind of algorithm `signature`? What about XOR and hash cyphers - how could someone find out that I've used one of those? I suppose the original and the encrypted text would be compared, but what kind of similarity is there to be found? Can it be reduced somehow?
> ciphered text should resemble, as much as possible, "white noise" (random text),
> and be also immune to frequency analysis.
Would any similarity in fequency analysis for the orginal and the encrypted text, yield any clues? Would it make any difference if there were multiple pairs of original and encrypted text (same algorithm, same key) available for analysis?
> I suppose the original and the encrypted text would be compared, but what kind > of similarity is there to be found?
Normally, what you search for are statistical anomalies.
> Would any similarity in fequency analysis for the orginal and the encrypted text,
> yield any clues?
Yes, of course, this is how frequency analysis works.
>Would it make any difference if there were multiple pairs of original and encrypted >text (same algorithm, same key) available for analysis?
Yes, definitely. One of the factors for the success of a known-plaintext attack is in the length of the sample used for decryption. It could go even better (or worse, depending on your role in the matter) if the attacker could freely choose the text to have encrypted, in order to make a confrontation with the plaintext.
I hope I was somewhat understandable. :)
Aleksandar BradarićSoftware DeveloperAuthor Commented:
Hi,
OK, I think I got the general idea of what I should do. As there will be multiple samples of original and encrypted text available, my only chance is to use a strong algorithm which makes the encrypted text as close to random text as possible...
Thanks :) Here are the points.
Take care,
Leannonn
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usually it is not possible, unless you are talking about really simple cryptography algorithms, such as rotation-, simple-hash and XOR-ciphers. Otherwise, ciphered text should resemble, as much as possible, "white noise" (random text), and be also immune to frequency analysis.
Cheers!