# Re: An hash-Encryption algorithm

*From*: Neo <neoscandal@xxxxxxxxx>*Date*: Sat, 28 Jan 2006 17:15:18 +0000 (UTC)

Kristian Gjøsteen <kristiag+news@xxxxxxxxxxxx> wrote in news:0hesa3-

abu1.ln1@xxxxxxxxxxxxxxxxxxxxx:

> Neo <neoscandal@xxxxxxxxx> wrote:

>>Kristian Gjøsteen <kristiag+news@xxxxxxxxxxxx> wrote in

>>news:uo7qa3-j1m1.ln1@xxxxxxxxxxxxxxxxxxxxx:

>>

>>> You are getting somewhere. Now you are just missing a somewhat

>>> subtle point: Encrypt two messages P1(1,...,n) and P2(1,..m) with

>>> the same key K(0). Find the expression for the first ciphertext

>>> blocks C1(1) and C2(1) and compute their exclusive ors. What do you

>>> find?

>>>

>>

>>Hmm.. according to my design that would imply ( consider

pa,ca,pb,cb)...

>>

>> ca xor cb = (pa xor (ka(0) + salt1)) xor (pb xor (kb(0) + salt2))

>>

>> |_______________________| |______________________|

>> ciphertext1 block 1 ciphertext2 block 1

>>

>>I dont see how this may be simplified...

>

> Now you have this thing called "salt" in there. It wasn't there

> yesterday!

It was!

------------copypaste start------------

>>K(0) = user entered key + salt (which is added plainly into the

>>encrypted file header)

>>

>>K(1) = MD5(K(0))

>>

>>C1 = K(1) XOR P1

>>

>>for n = 2 onwards..

------------copypaste end--------------

>

>>Note that salts are generated at the time of encryption .. and

>>thoeretically no two salts would match. Thus no two encryptions would

>>use similar keys during the first round.

>

> Exactly. You need to be a bit careful about how you add your salts to

> the message. The above looks a bit shaky.

Hmm.. what would be a "non-shaky" version of adding the saly. XORing

perhaps?

>

> Your "salt" is commonly called a nonce or iv in this context:

>

.

**Follow-Ups**:**Re: An hash-Encryption algorithm***From:*Kristian Gjøsteen

**References**:**An hash-Encryption algorithm***From:*Neo

**Re: An hash-Encryption algorithm***From:*Neo

**Re: An hash-Encryption algorithm***From:*Kristian Gjøsteen

**Re: An hash-Encryption algorithm***From:*Neo

**Re: An hash-Encryption algorithm***From:*Kristian Gjøsteen

- Prev by Date:
**Are Our Political Leaders Really as Mad as We Suspect? Read Here!** - Next by Date:
**Re: *** surviving my new CANCEL attack***** - Previous by thread:
**Re: An hash-Encryption algorithm** - Next by thread:
**Re: An hash-Encryption algorithm** - Index(es):