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Questions tagged [rc4]

RC4 is a fast and simple stream cipher used correctly in SSL and incorrectly in WEP.

13 questions with no upvoted or accepted answers
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Does the bias in RC4 drop asymptotically further in the keystream?

It's well-known that the RC4 keystream has significant biases that become less prominent later in the keystream. The most severe bias is in the second byte, which has a 128-1 bias towards zero. Other ...
6
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0answers
112 views

What is the “brand X” cipher mentioned in the Usenet thread about RC4?

In the original Usenet thread about RC4 when it was finally reverse engineered, a user by the name of Michael Johnson mentioned that the RC4 algorithm looked surprisingly like another proprietary ...
3
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0answers
110 views

Can a stream cipher with a big S-box create ASIC-resistance?

For a proof of work system a hash algorithm generates one pseudorandom index each round, in the same manner as RC4 and Spritz do. And it uses a bigger S-box, e.g. 2^20 numbers. The actual hash would ...
3
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0answers
2k views

Understanding the FMS attack on WEP

I am trying to implement the Fluhrer, Mantin and Shamir attack, one of the ways to break WEP. I seem to have hit on a problem. I have no idea whether or not it is a programming error, or if I don't ...
2
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0answers
119 views

Extracting RC4 and 3DES keys from system memory

I have read papers [1], [2] that have presented techniques on extracting symmetric encryption keys from memory during the process of encryption. There are tools [3] that can extract AES keys from ...
1
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0answers
77 views

Randomness Test of Permuted Sequence

As we can generate a permuted sequence using KEY in KSA (Key Scheduling Algo) of RC4. Is there any way to check the randomness of the permuted sequence? Let say I created 100 different permuted ...
1
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0answers
123 views

Understanding a security error with RC4 using the same key to encrypt on the client/server sides

This apparently was a bug with WhatsApp a while ago. I am endeavoring to recreate it and understand it. The bug had to do with the fact that the same key was used to encrypt plaintext on both the ...
1
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0answers
1k views

RC4: Find the complete plain text of a ciphertext when we know part of the plaintext

I need to decrypt an encrypted file with RC4 to answer to a Internet challenge. The file in question is a dump of a Teensy ROM and it is completely encrypted. Luckily, it looks like it's a standard ...
1
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0answers
117 views

WEP: Why is the challenge string randomized?

In WEP, the 128-bit challenge string generated by an access point would allow for approximately 340 undecillion unique strings. Would it be problematic were a string to be reused? I suppose with $2^{...
1
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0answers
38 views

How to calculate LOW(b) and HIGH(b) in spritz cryptography

I try to implement spritz cryptography like this paper . But I don't know how to calculate LOW(b) and HIGH(b). In paper page 7. ...
1
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0answers
348 views

What RC4 key value will completely invert $S$ after initial permutation?

What RC4 key value will completely invert $S$ after the initial permutation, so that $S[0] = 255, S[1] = 254, …, S[254] = 1, S[255] = 0$?
0
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0answers
44 views

Recreate RC4 Stream cipher

I'm trying to learn how to go about cracking RC4 ciphers (nothing illegal, its an old, i.e., not active challenge for a job application, so no cheating). I have nine md5 hashes with their own ciphers. ...
0
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0answers
74 views

RC4 via nonlinear mixer — sound?

We implemented a rc4 (ARC4) variant for creating a cryptographic stream - question is: Is this sound? (I'll give an example for 32 bit variant, though 64 bit/larger is possible) Algorithm is as ...