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cipher/ decipher with 3DES alg

Posted: Wed Apr 26, 2017 11:46 pm
by Ruenie
Hey guys,

I came across a problem recently. Hope you can figure me out.

I tried to cipher some text with 3DES alg with a key of 16 bytes. And I asked users to input the first part of my 16 bytes key - that is 8 characters. The second part is hard-coded.

I tried with simple key like "12345678". It ciphers without any problem. So I expected that the result could only be deciphered with that key. But the fact proved that what I thought was wrong. I can also decipher with a similar key, like "12345679".

Can anyone figure out the reason why this happened?

Thank you so much.

Re: cipher/ decipher with 3DES alg

Posted: Thu Apr 27, 2017 4:17 am
by chico0609
It seems that your problem has something to do with DES weak key. Do you use weak key?

Re: cipher/ decipher with 3DES alg

Posted: Thu Apr 27, 2017 6:01 am
by Ruenie
I didn't use any weak key. Except 3DES, can I use other algorithms?

Re: cipher/ decipher with 3DES alg

Posted: Fri Apr 28, 2017 4:23 am
by chico0609
Try to use AES instead.

Re: cipher/ decipher with 3DES alg

Posted: Fri Apr 28, 2017 6:17 am
by tay00000
Provide sample code so that accurate advice on the problem with your 3DES implementation can be given. With only your brief description, nobody is able to properly visualize the problem.