Questions tagged [rc4]
RC4 is a fast and simple stream cipher used correctly in SSL and incorrectly in WEP.
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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^{...
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Combined message separation?
I have two ciphertexts, I suppose that its RC4 with reused key. I have XORed both ciphertexts and obtained message containing combined cleartexts.
I suppose that the underlaying messages are written ...
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Stream Ciphers -- Need clarification on their benefits in practice
Compared to a block cipher which encrypts 16 bytes at a time, stream ciphers can encrypt a byte at a time. I am curious about which applications would immensely benefit from the ability to encrypt a ...
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Does RC4 continue to be used anywhere?
RC4 in TLS is now broken. But the breaking seems to have a lot to do with how web transactions work in general. Is there any application outside of the web where RC4 is still used? I know that WEP is ...
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When is AES chosen instead of a stream Cipher (e.g., RC4) during an SSL connection?
During an SSL handshake, the browser sends a list of cipher suites to the server, from which the server selects one option.
For data encryption, two of the several possibilities for the ciphers in ...
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Mitigating weaknesses in RC4 [duplicate]
I've been researching RC4 and implementing it, and I was wondering, from the perspective of a cryptographer (a real one, not a fake one like me), what could be added to the RC4 algorithm to improve on ...
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Can stream ciphers (usually) be "run backwards"?
Is it possible to reconstruct the previous output bits of a stream cipher, e.g. RC4, when only the current state is known, or is that computationally hard, or even impossible (due to ambiguous ...
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What is the PRG period of stream ciphers such as RC4 or Salsa20?
I am confused about how long a stream cipher can be used before you should change the key. To be concrete, let me use the stream cipher based on RC4 as an example.
Let's say I want to encrypt a very ...
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How are constructs with data-dependent swaps and rotations cryptanalyzed?
Linear and differential cryptanalysis seem well suited for constructs with a (relatively) simple fixed structure of boolean expressions. But some ciphers incorporate swaps of array elements where the ...
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RC4 using a key without nonce's or IV's [duplicate]
I'm researching RC4 and I am trying to recreate a condition where RC4 is crackable. However I can't quite find the article/resource I need to find the weakness for an implementation like this (python):...
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How do attacks on WEP work?
There is an abundance of tools and tutorials on how to break WEP encryption. However, I fail to find a nice resource that gives a clear break-down of why the attacks are possible. For example, I know ...
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Two or more initialization vectors with the same key
I'm studying about WEP and I'm in doubt.
It seems that because it uses a initialization vector of 24 bits, which is relatively short, is easy to determine which key was used to encrypt the data.
But ...
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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 ...
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finding key from given ciphertext and open text
very new to crypto-stuff, i have to write a program in C that compute key(k) used in RC4 when I know open text(p) and ciphered(c) text
so I have c_1=p_1 XOR k. How ...
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Does omitting the first two lines of RC4's pseudo-random generation algorithm weaken the cipher?
A particular educational software program published by a U.S. government agency uses a variant of RC4 to obfuscate its data files (see Stack Overflow question). The variant of RC4 in question is ...
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Are there known practical attacks on RC4-dropN? [duplicate]
RC4 is known to leak information about the first few bytes of the ciphertext due to keystream biases.
However, are there known attacks on RC4-drop[N] where N is large enough, that leak information ...
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Do we have anyway of knowing if avoiding self-permutation in RC4 makes it any stronger?
OK, so lots of questions get asked about RC4 but I want to make mine specific and hopefully answerable.
RC4 Design as I'm sure anyone reading this knows, uses self permutation in stage 1 of the KSA.
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How much stronger is RC4 if it is keyed with an RSA private key?
My idea is to generate a RSA 2048 bit key and use RC4 with the private RSA key to encrypt a stream of data. RC4 is weak because RC4 keys are small, 256-bit. But when we use RC4 with private RSA 2048 ...
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Is it secure to use ciphertext feedback with RC4?
Consider the following modification of RC4 to give some "ciphertext feedback"
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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.
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Is RC4 +XOR secure for small data?
I need to encrypt transmission between my device (with AVR processor) and base. I create packet data - it will be encrypted into string:
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Double Encrypting with two different keys
In terms of security, would it be MORE or LESS secure to take, say, an RC4 output (or Serpent) or other, that is encrypted with one key, and to encrypt that output with AES (using a different key)?
<...
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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 ...
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Safety of AES ECB when used with openssl_seal function
I'm trying to use PHP to encrypt files with a public key. I'm using the function openssl_seal that "encrypts data by using RC4 with a randomly generated secret key."
RC4 is considered unsafe so the ...
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Question about the key in RC4
I am planning to develop a more secure version of the RC4 algorithm. Since I´m not an encryption expert, I´ld like you to help me find answers to the following questions:
Does the value of the key ...
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Why does "2xAES-256" provide "99.99%" security strength whereas "1xAES-128" provides "40%"? [closed]
I recently was "directed" to FlipsCloud, a company selling security solutions (as far as I can tell).
In particular I've investigated their page and found a page on their "encryption features".
This ...
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What happens when a RC4 stream gets corrupted?
I want to encrypt a large file using RC4. But what happens if the encrypted file gets corrupted (bytes modified or lost)? Can I still decrypt the rest of the file correctly?
If not, what is the best ...
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What is the period of a cipher?
For the following explanation of RC4:
It is a variable key-size stream cipher with byte-oriented operations. The algorithm is based on the use of a random permutation. Analysis shows that the ...
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what are the plaintext's for the RC4 stream cipher test vectors in RFC6229?
https://www.rfc-editor.org/rfc/rfc6229 has stuff like this:
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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 ...
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RC4 encryption/ decryption with hashing
I am working on RC4 encryption/ decryption algorithm based on the following:
A wants to send M to B, for that A did:
H = Hash (K||M)
C = Ek (M||H)
A sent ...
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Does a stream cipher require a KDF when it's key is variable length?
RC4 has a variable length key. Is it still necessary to use a key derivation function, such as PBKDF2, to initialize it?
Would using a single character password weaken it's output when compared to a ...
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RC4 key schedule and algorithm design
I've looked up RC4 algorithm and it's seems easy enough but some parts of it seem random to me.
In the key schedule part take for example the following part :
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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 ...
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How should I treat a new cipher release like Spritz?
I have been looking at both the paper as well as the sourcecode of Spritz — a spongy RC4-like stream cipher and hash function by Ronald L. Rivest and
Jacob Schuldt.
The paper states
We have also ...
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Google is using RC4, but isn't RC4 considered unsafe?
Why is Google using RC4 for their HTTPS/SSL?
$ openssl s_client -connect www.google.com:443 | grep "Cipher is"
New, TLSv1/SSLv3, Cipher is RC4-SHA
Isn't RC4 ...
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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 $S[0] = 255, S[1] = 254, …, S[254] = 1, S[255] = 0$?
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Is TLS_RSA_WITH_RC4_128_SHA still a secure cipher to use? [duplicate]
I have read numerous times that the RC4 cipher itself is considered broken in TLS. Still many websites are using the TLS_RSA_WITH_RC4_128_SHA configuration even to date.
Now, I know that sometimes ...
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Why Distance-128 relation in Plain texts is reflected in Cipher texts
The two text having relation as "\x10\x11" → "\x90\x91" (80+10) will have relation after encryption/decryption also in RC4. Following code clearly describes the problem I am mentioning.
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Is RC4 a problem for password-based authentication?
This is a follow-up question to Does TLS use RC4-drop[n]?.
As mentioned in section 6 of RFC4345, there are weak distinguishers for RC4 keystreams available that even work for keystreams that ...
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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 ...
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Does ssl_rsa_with_rc4_128_md5 have known weaknesses?
My bank's website uses HTTPS with the cipher suite ssl_rsa_with_rc4_128_md5.
What are the known weaknesses of this suite? Do they have a practical impact for ...
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Can you help me understand how RC4-52 is done using pen-and-paper?
I've played a lot with VIC and enjoy its complexity and effectiveness as a field cipher. However, RC4 has caught my attention lately and I've read there is a RC4-52 variant that can be done by hand.
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RC4 : Keystream reconstruction?
First up: it's a step in some challenge found on the Internet, where we get an application and a file. The application must be feed with that file and a password (the password is the flag for the ...
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Which stream cipher can we replace the RC4 in the SSL?
In cryptography, the Fluhrer, Mantin and Shamir attack is a particular stream cipher attack, a dedicated form of cryptanalysis for attacking the widely-used stream cipher RC4. The attack allows an ...
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Can two rc4 encoded messages be XORed and decrypted if encrypted with the same key?
If I have the following:
E1 = RC4(M1, K);
E2 = RC4(M2, K);
If two different messages M1 and M2 are encrypted with the same key, K, can the key be recovered by ...
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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 ...
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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 ...
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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 ...
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Simple RC4 key generation scheme
I would like to ask you about your opinion on the following scheme of combining a master key and a nonce and stretching the result to the full 256-bytes RC4 key.
Master key $K_m$ is a pre-shared ...
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