Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [rc4]

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

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Is RC4 secure with a single-use 32-byte random key prefix and 3072 prefix bytes discarded?

Are there any known attacks against RC4 if used with a single-use, random-generated 32-byte key, and 3072 random bytes prepended to the plaintext? Are there any reasons why we should consider such a use of RC4 less secure than an other…
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Does "double RC4" exhibit the same weaknesses as standard RC4?

I know that RC4 is weak. However, I don't know if two RC4 streams XORed with each other can be attacked in the same way that one can, especially if $n$ bytes are dropped. Assume keys and IVs are independent and random. (This is purely theoretical,…
Demi
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Explain the 'Breaking 104 bit WEP in less than 60 seconds' paper

Could you explain the 'Breaking 104 bit WEP in less than 60 seconds' paper, without skipping too much technical details. Could you an answer questions, like: how is '1.24/256' a significant difference compared to '1/256'? And how this seemingly…
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How was 256-bit WEP cracked as well?

WEP is now considered as insecure. But how about the 256-bit WEP? Could someone explain why a 256-bit encryption isn't enough? 'A 256-bit WEP system is available from some vendors. As with the other WEP-variants 24 bits of that is for the IV,…
user129789
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What are the steps for decryption of RC4?

I've seen a lot of algorithms posted everywhere about how to encrypt using RC4. For example, this wiki article https://en.wikipedia.org/wiki/RC4 explains the KSA and PRGA steps. After it generates bytes, they are XOR'd with a message to encrypt the…
user2072374
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Is it possible for an element to be swapped with itself in RC4?

Given the design of RC4, is it possible or impossible for the values $i$ and $j$ to be equal to each other when $S[i]$ and $S[j]$ are swapped?
Melab
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simulating rc4-256 with rc4-128

OpenSSL supports rc4 with 128-bit keys and rc4 with 40-bit keys. It does not support rc4 with 256-bit keys. My question is... is it possible to modify the state of the pseudo-random generation algorithm (PRGA), given a 128-bit key, to match the…
neubert
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Do Export Restrictions Still Apply To The Key Length of RC4?

I've just read a paper from 2004 which stated that the RC4 encryption algorithm was restricted to a 40 bit key size when exported from the USA; however the reference for this information (Applied Cryptography - Schneieir) was published in…
slickboy
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RC4 - Key scheduling Algorithm

I'm trying to understand the KSA algorithm of RC4 which apparently scrambles the array which will later be used by the PRGA to generate the keystream. My question is, does the seed used by the KSA have to be kept secret?
Trey
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RC4 S-Box and Keystream

I'm studying the RC4 algorithm and I have the following questions: On all questions assume that an expanded (2048-bit) key is used, and that the first 4096 bytes of the KeystreamIm are discarded. After the above process, is the resulting S-box…
Devros Exrix
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Recovery of RC4 key when S-box 0 stage or 1st stage known

I've been exploring around, trying to understand if such thing is even possible. I have some RC4 ciphertext which I know it's plaintext and I would like to extract the key just from cipher and plaintext. While reading through "RC4 Stream Cipher and…
devdc
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RC4 system pitfalls

A system fell into my neck, where lots of files are splitted into several segments and encoded via RC4. RC4, because client side - slow computer, slow flash arithmetic ops - can only decode big blobs with this simple algo in a reasonable amount of…
MollyRazor
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I need a simple cryptographic code to put on a t-shirt

I never worked with cryptography but I wanted to add an easter egg on the design I'm making for a t-shirt. I need it to have a key that will be embroided on the front design wich is: 15122017 that can be used to decrypt the text that is in the…
artemocdr
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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 client and server sides. However, (A ^ X) ^ (B ^ X) =…
R. Rengold
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Do these 2 KSA shortcuts weaken RC4?

Alice securely gives Bob a secret key so they can exchange 10 different messages encrypted with RC4. (Messages will include a counter for uniqueness and a MAC for authentication.) For each message exchange, Alice and Bob both start by permuting…
Witness Protection ID 44583292
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