Symmetric cryptosystems assume two communicating entities share a pre-established secret key.

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Homomorphic encryption based on XOR

Consider the values $a$ and $b$ are encrypted as $c_1=(a \oplus D)$ and $c_2=(b \oplus D)$. My question is: can we derive $b+a$ from any combination of $c_1$ and $c_2$? Note: I admit that the ...
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Number of possible keys in a Play fair cipher [duplicate]

So for the play fair case, the number of possible keys is : 26x26 = 676 possible keys But if we consider the repeated letters, how many unique keys will the play fair have? I mean how will ...
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Attacking both authenticity and secrecy in authenticated encryption modes

looks like NIST only approved GCM mode for authenticated encryption and other modes don't have any approval or a good implementation available. Is that possible a weakness in $GHASH$ compromise ...
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72 views

The specification of modern, non-communicating cipher machinery [closed]

I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed. Consider powerful electronic machinery which remains in the custody of communicating ...
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518 views

Guessing encryption algorithm based on key and ciphertext

Is it possible to tell which encryption algorithm was used, assuming I have a key and a encrypted text? To not complicate the situation let assume we are speaking about symmetric algorithms only. ...
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238 views

Is symmetric encryption no longer necessary?

Here is it: Symmetric encryption is no longer necessary, because all security services can be implemented with public-key cryptography. Moreover, in public key cryptography the operations for ...
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1answer
104 views

OTP - Reuse key BUT add IV, is it secure enough?

EDIT: REUSING KEY IS SECURE! OTP - Reusing key IS SECURE! PROVED! I have already asked a similar question and now I can continue to this question about adding a "extra key" = IV. My last question ...
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1answer
150 views

OTP - Why not reuse key? EDITED! [duplicate]

EDIT: REUSING KEY IS SECURE! OTP - Reusing key IS SECURE! PROVED! This might sound really dumb but why is it bad/insecure too use the same key twice on One-time-pad? Question: Why and how does using ...
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List of available symmetric & assymetric ciphers [closed]

I was looking all over the Internet list of ALL existing symmetric and asymmetric ciphers. I know that there's, for example, AES, DES, Blowfish, DSA. But how about more? Where to find such list?
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how to integrate 2-3 algorithms to encrypt large data fastly and securely insted using AES? [closed]

I am thinking to build an encryption algorithm which take less time when encrypt large data such as video,mp3 and which has security credential.
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Found a way to crack AES-128, what now?

Let us assume the following scenario: I have just found a way to crack AES-128 in a reasonable time (1-2 days). How do I publish and prove this? I remember reading about lots of people who cracked ...