Hi,

I have been given a code without the key to crack. I have been told that it is based on primes numbers and the code is made up of all letters. Any ideas where I should start? Is there some known maths formulas to try?

Thanks.

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- September 20th 2011, 11:36 PMmark090480Decrypt code without the key
Hi,

I have been given a code without the key to crack. I have been told that it is based on primes numbers and the code is made up of all letters. Any ideas where I should start? Is there some known maths formulas to try?

Thanks. - September 20th 2011, 11:56 PMchisigmaRe: Decrypt code without the key
Supposing thet You know the 'coding algorithm' but You don't know the key, then the code is 'perfectly sure' only if the following conditions are satisfied...

a) the key is 'perfectly random'...

b) the key has been used only for one message...

If a) or b) aren't satisfied, then Youn have 'some chance' to decrypt the message...

Kind regards

- September 21st 2011, 12:07 AMCaptainBlackRe: Decrypt code without the key
- September 21st 2011, 12:25 AMmark090480Re: Decrypt code without the keyQuote:

a) the key is 'perfectly random'...

b) the key has been used only for one message...

So the only way is to go through all algorithms? I understand that there should be some logic involved. - September 21st 2011, 12:29 AMCaptainBlackRe: Decrypt code without the key
- September 21st 2011, 12:37 AMmark090480Re: Decrypt code without the key
It is a question to learn about cryptography and computer languages. All I know is that it's based on primes, no more. The computer language does not matter, the algo is what counts.

- September 21st 2011, 12:57 AMchisigmaRe: Decrypt code without the key
In order to avoid misunderstandings as 'perfectly random key' one means that the key must have

*the same lenght of the message*[if not the key is*repetitive*and not 'perfectly random'...] and it*must have some basic statistical properties*[about that may be a detailed discussion has to be made...]. If part of the message for some motivations is known, then if the conditions a) and b) are satisfied the remaining part of the message 'with high probably' remains unknown [also about this point a detailed discussion may be useful...]...

Kind regards

- September 21st 2011, 01:04 AMchisigmaRe: Decrypt code without the key
- September 21st 2011, 01:06 AMmark090480Re: Decrypt code without the keyQuote:

one means that the key must have the same lenght of the message

- September 21st 2011, 08:49 PMCaptainBlackRe: Decrypt code without the key
- September 6th 2012, 03:32 PMhumbleRe: Decrypt code without the key
"i have a cipher text to decryp. I have tried it a lot but i couldnot, i want ur help.More over i dnt knw the key and encryption technique used for it. if u plz help me. i would b vry thankful to u.