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

learn more… | top users | synonyms

2
votes
1answer
46 views

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 ...
1
vote
0answers
25 views

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 ...
3
votes
2answers
217 views

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 ...
8
votes
3answers
1k views

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 ...
0
votes
0answers
26 views

RC4 Encrypting Plaintext, Key of 3 Bytes [closed]

Good afternoon! I tried to Encrypt a Plaintext of length of 3 Bytes with the Key of length of 3 Bytes, but it gave a wrong Ciphertext as I can't receive same Plaintext during Decryption process. I ...
6
votes
2answers
222 views

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 ...
0
votes
0answers
35 views

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):...
1
vote
1answer
62 views

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 ...
4
votes
2answers
112 views

Is the RC4 keystream random or not?

I have cause to use the PRNG half of RC4, but am seriously confused as to the randomness of its output. (Only the PRNG half.) On the one hand, there is a large body of literature finding ever ...
3
votes
1answer
44 views

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 ...
6
votes
1answer
79 views

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 ...
-1
votes
1answer
32 views

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 ...
6
votes
1answer
622 views

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 ...
1
vote
0answers
18 views

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 ...
5
votes
1answer
146 views

Can somebody help me understand RC4 Spritz? (Three Questions)

So ever since I first took a stab at understanding stream Ciphers, not one stood out more than RC4, because it's so fantastically simple. As most people reading this will know, with its fantastic ...
5
votes
1answer
112 views

Are there any long term RC4 bias based exploits?

The RC4 cipher possibly exhibits low level bias in it's long run PRNG keystream. I'm specifically excluding short term bias attacks which I'm defining as outputs < 1024 bytes. Are there any real ...
4
votes
2answers
99 views

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. ...
0
votes
1answer
107 views

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 ...
2
votes
1answer
47 views

Is it secure to use ciphertext feedback with RC4?

Consider the following modification of RC4 to give some "ciphertext feedback" ...
1
vote
0answers
16 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. ...
0
votes
1answer
386 views

Encryption Algorithms in Verilog code

Can we implement Encryption Algorithms like RC4,AES and DES in Verilog? if no what are the limitations?
0
votes
1answer
294 views

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: ...
2
votes
2answers
2k views

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)? <...
0
votes
0answers
40 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 ...
3
votes
1answer
213 views

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 ...
2
votes
2answers
220 views

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 ...
4
votes
1answer
605 views

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 ...
0
votes
1answer
1k views

RC4 , Is it possible to find the key if we know the plaintext and ciphertext?

Is it possible to find the key if we know the plaintext and ciphertext with RC4. How should I write the algorithm?
5
votes
2answers
242 views

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 ...
2
votes
1answer
368 views

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 ...
1
vote
2answers
42 views

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 ...
0
votes
0answers
67 views

emulating progressive encryption with RC4 / OpenSSL

PHP's OpenSSL bindings do not support progressive encryption by default. ie. if you do ...
1
vote
1answer
324 views
1
vote
1answer
93 views

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 ...
0
votes
1answer
323 views

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 ...
3
votes
2answers
175 views

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 ...
5
votes
1answer
829 views

Security analysis of Spritz?

Recently, a new cipher called Spritz has been released by Ronald L. Rivest and Jacob Schuldt. It should be a "drop-in replacement" for RC4. There are many differences to RC4, Spritz is "spongy" and ...
2
votes
1answer
318 views

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 ...
2
votes
1answer
221 views

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 : ...
2
votes
0answers
774 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 ...
1
vote
1answer
614 views

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 ...
41
votes
7answers
24k views

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 ...
1
vote
0answers
170 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 $S[0] = 255, S[1] = 254, …, S[254] = 1, S[255] = 0$?
1
vote
0answers
26 views

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 ...
1
vote
1answer
43 views

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. ...
10
votes
2answers
392 views

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 ...
1
vote
1answer
305 views

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 ...
6
votes
2answers
3k views

RC2, RC4, RC5 key length

While reading the Wiki page on RC4 I noticed that the key size must be in the range of 40–2,048 bits. So should I understand like this, that I can have a key that has length of, lets say 333 bits? (...
0
votes
1answer
3k views

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 ...
2
votes
1answer
423 views

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. ...