Questions tagged [rc4]

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

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RC4-40 with IV (32-bit) setup

I have taken this implementation of RC4 written in C. I have 40-bit key and 32-bit IV (both in hex). So, questions is about KSA step: How should I transform hex key value into the char array? Just ...
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How can I decrypt an RC4 encrypted text when knowing the first 8 characters of the plain text secret?

I'm having difficulty decrypting a secret message as a part of a CTF and I was wondering how could I decrypt an encrypted text that has been encrypted with pycrypto RC4 and when the first 8 characters ...
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RC4: Known plaintext key, unknown key derivation

I am working with an older piece of software that generates encrypted backups that I'd like to decrypt. I have a plaintext key, a few examples of encrypted data and I'm pretty sure the data is ASCII, ...
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Why are des-cbc-hmac and rc4-hmac-exp considered weak in kerberos?

Kerberos uses des-cbc-hmac (mac and encrypt) and rc4-hmac-exp based on md5 (mac and encrypt I think) in their encryptions. Those encryptions are considered as weak and should not be used. Why are they ...
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What authenticated encryption do kerberos use in windows?

I have learned about the kerberos protocol and seen that the windows version uses a couple of authenticated encryption schemas (like rc4-hmac-md5). What type of authenticated encryption is it? Is it a:...
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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 ...
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MS CryptoAPI RC4-1024 vs AES-128?

I'm trying to figure out MS CryptoAPI to generate a symmetric key on one computer then an RSA key on another, send over that public key to use to export the symmetric key to that other computer. I'm ...
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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. ...
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How to generate the Keystream from IV+Key in RC4

So I understand that a keystream is generating from a key and is the length of the message you want to send, so that you can properly XOR every bit. But I'm having trouble finding and understanding ...
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If two hosts are using a transparent IP level authentication and encryption, is their communication subject to both MITM or replay attacks?

Encryption process for any outgoing packet to the specified "remote IP": -original payload P is encrypted (the bytes after the IP header) using RC4 with the preestablished key ...
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Use large key size for RC4 to avoid RC4 bias

I saw a question on StackOverflow where RC4 was initialized by a 1024 bit key (with 2048 the maximum key size, if I'm not mistaken). Will such a large key size possibly solve any of the bias of the ...
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Books about stream ciphers

I am new to ciphers and for my assignment i have to implement a stream cipher algorithm without libraries (on my own). So my question is: Does anyone know about any GOOD books which have examples and ...
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Are there ready-to-use software that can try many decryption techniques on a ciphertext, with no information?

Let's say I receive a 1 MB encrypted file, but I get no information about the encryption method, and no password. The only thing I can guess is that the person probably used a weak encryption method ...
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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 ...
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Attacks against RC4 when index $i$ is unknown

RC4 uses two 8-bit indices. One, $j$, is key-dependent and secret, and the other, $i$, increments by one for each byte output. The $i$ index is typically considered to be public, but what if the RC4 ...
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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 ...
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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 ...
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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 ...
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Difference between RC2, RC4, RC5 and RC6

Can anyone point out the core differences between RC variations?
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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 ...
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Arbitrary key size in RC4

Is it possible using RC4 that for e.g. a 17-bit long plaintext i can get a 17-bit long ciphertext? From my understanding, for this example i need a 17-bit long key to do the XOR operation for ...
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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 ...
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Why does Blowfish and RC4 (Arc4) make same encrypted strings [closed]

I made a program on android. I used a password key of "PBKDF2WithHmacSHA1" for both of them as a key. The program i made was using Android java Cipher library. When I encrypt and decrypt with blowfish ...
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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 ...
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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 ...
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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 ...
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Is RC4 cipher just xoring plaintext with a random sequence seeded by key?

After reading about RC4, it seems that it's nothing else than: the plaintext stream is just XOR'ed with a pseudo-random sequence that is initialized/seeded with the key Is there something else in ...
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How should k2 be produced in the RC4A stream cipher (A modification of RC4)?

RC4A is a slight modification of the simple RC4 stream cipher designed to strengthen it against a number of attacks. Here's that paper. However in the paper, the second key ...
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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?
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Are Two Ciphers Better Than One? i.e. RC4 and AES

OK It's cringe time (or hopefully not) I know this is probably a variation of an old and dragged out question or so you may think but let me ask away and hopefully get some insight. Google a while ...
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Incremental RC4 algorithm?

I am currently analysing a client-server application which apparently uses RC4. I've got the secret key and nonce and I was very surprised about the approach they encrypted the packets. Since I am no ...
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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 ...
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3 answers
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Using a PRNG for a stream cipher instead of a dedicated algorithm

I am aware, that it is possible to build a stream cipher using some deterministic PRNG (like HASH_DRBG or CTR_DRBG) with good key material as the seed. What are the advantages of using a purpose ...
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RC4, finding key if we know plain text and ciphertext [duplicate]

Having plain text A , and cipher text B. Can we somehow retrieve key , when we want to decrypt text C which was also crypted with the same key?
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Is the RC4 KSA the same as an extractor?

I am studying the RC4 stream cipher, particularly when it used to be applied in the TLS/SSL protocol. Is it safe to say the KSA acts like an extractor taking in the shared secret key, k (between ...
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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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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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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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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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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 ...
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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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9 votes
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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 ...
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