# Questions tagged [brute-force-attack]

A brute-force attack is attempting to find a secret value by trying all possible values until the correct one is found.

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### Is a larger block size less secure against a brute-force known cipertext attack?

Suppose a ciphertext $c$ was encrypted from plaintext $m$, and we know something about the form of $m$; say, for example, that $m$ is English text. We can attempt to brute-force $m$ from $c$ by ...
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Meet-in-the-middle attacks are used to justify that attacks on ECC and double encryption will have complexity of $O(\sqrt{n})$ for ECC and $O(2^{n+1})$ for double encryption complexity instead of $O(n)... 1answer 91 views ### Msieve & Yafu - RSA Exponents and bruteforcing I am a layman in regards to the math behind RSA (and in general, relatively), and my goal is to bruteforce a large quantity of 512-bit RSA keys. Having searched around, I see that msieve, yafu, and an ... 1answer 60 views ### Any known cases of lucky collisions resulting in security breaches? This isn't a deep technical question, but I feel like this is a good place to ask. Modern cryptography generally rely on statistical chances of collisions according to current computing powers. Are ... 1answer 80 views ### Complexity of a brute-force search I am currently thinking about the complexity of a brute-force attack on a cipher. Let the key length of the cipher be 64 bit. Then there are$2^{64}$different keys in the keyspace. If you do a brute-... 1answer 567 views ### Security levels in NIST Post-quantum project: e.g. AES-128 vs SHA-256 In an article about NIST Post-quantum Standardization project I read about the security criteria of the proposed schemes and there was this table (Level I lowest security, level V highest): Level I: ... 1answer 44 views ### Is it possible to narrow down the possible keys used for AES CBC encryption, knowing a given plaintext and its ciphertext, where IV=0? [duplicate] I'm brute forcing a ciphertext with a given dictionary to figure out which key was used. However, it's been hinted at that there is a way to narrow down the dictionary to a smaller subset of ... 1answer 78 views ### Estimate password cracking time given Shannon Entropy Is there some algorithm that, given the Shannon entropy of a string, compute an estimation of the time that an average home computer will take to crack the password? Thank you. 1answer 31 views ### Vulnerability of low value generated key I have read here that Elgamal is resistant to brute-force attack, because the group to where the key is selected is very large. But since the key generation is random, (i assume)there is a chance that ... 1answer 87 views ### Security implications of using a high entropy password with a low iteration count for a key derivation function This question is related to my other question, but also this entropy calculation question as well as this article about PBKDF2. It may also be considered as a duplicate of this question, although in ... 2answers 49 views ### How to protect against brute force attacks in the case of a small dictionary? Sorry if I'm not using the right terminology, as I'm new to crypto. I want to know the most effective way to protect a database against brute force attacks in the case of a small dictionary. For ... 4answers 251 views ### How is PBKDF2 so much better than normal Hashing or even using HMAC I do not know how the Key Length extension attack works. So if we leave that aside for once, and say just about usual brute-force attack on the hash, I don't really know how is PBKDF2 so much better ... 4answers 186 views ### Is an invulnerable code possible (including brute force attack)? If I double encrypted a text with for example AES wouldn't it be invulnerable to bruteforce attacks due to the computer not knowing when it has reached the plain text? Plain text->1st layer of ... 2answers 1k views ### Why this brute force attack doesn't reduce all cryptographic hash functions' security bits against collision attacks to N/3? The traditional brute force collision attack is generate$2^{N/2}$(unique) random strings, hash them and this results in ~50% chance for collision. The attack talked in the question's title is ... 1answer 89 views ### Would it be easier to bruteforce the original data if given two hashes (from different hash functions)? [closed] I have a chat server which uses public keys to identify their clients. But if the public key is known, then everyone can send a direct message (DM) to each other, which is annoying. The clients should ... 1answer 97 views ### Bitcoin mining nonce and birthday attack Having read the basics of mining and this about SHA256 (probabilistic?) partial preimage possible? and SAT solving - An alternative to brute force bitcoin mining, I have the following question: ... 1answer 45 views ### Simplifying Meet-In-The-Middle Attacks Considering the fact that a block cipher is a bijective function on the set of possible plaintexts, if one views the encryption of a datum with a key$K_2$, which has been already encrypted with the ... 0answers 30 views ### Does the oracle have to have access to the encryption key to the padding oracle attack to work (CBC & PKCS#7)? Does the oracle have to have access to the encryption key to the padding oracle attack to work (CBC & PKCS#7)? I tried much to get a attach to work, but the oracle doesn't have access to the ... 0answers 57 views ### Can$AES_{k1}(m)$be equal to$AES_{k2}(m)$? [duplicate] Context: We have a generic bloc cipher composed of an encryption function$E_k$and a decryption function$D_k$operating on blocs of$n$bits. For a key$k$fixed, we can see$E_k$as a pseudo-... 2answers 449 views ### 19 out of 24 words of BIP39 passphrase (brute-force last 5?) I have managed to lose 5 words of my 24 word Ledger Nano S recovery phrase. I have words 1-19 but I am missing words 20-24. I have significant holdings on the wallet so would very much like to recover ... 1answer 93 views ### The small key-search circuit for brute-force of Bernstein I'm trying to understand Understanding brute force by Bernstein. I couldn't understand how the described machine can brute force the AES. The attacker builds a very small key-search circuit. The ... 1answer 47 views ### How to get a speedup linear in the number of iterations on unsalted iterated password hashing? In their 2015 paper "More Rounds, Less Security?" Guo, Jean, Mouha and Nikolić claim in section 5.4 that one can recover a password$P$given hashes of$D$different passwords generated from$H^k(P)$... 1answer 88 views ### Attack on a Feistel Cipher given the key and half of the ciphertext Consider a classical Feistel Cipher, with the round functions given and the keys used in the ciphering process. Is it possible to reconstruct the original data if half of the ciphered text is given? ... 1answer 100 views ### Comparing Shanks' Algorithm to Brute Force I'm trying to understand how/why Shanks' algorithm solves the discrete log problem$y=g^x \bmod p$faster than a brute force search does. Any explanation would be great. 0answers 70 views ### Aes brute force when part of data known [duplicate] I have buffer of 16 bytes that encrypt with AES 128 cbc with IV =000000......(all IV is 0) I have the encrypted buffer, and I know 7 bytes from 16 bytes before the encryption , I dont know the key . ... 2answers 129 views ### Can you encrypt a 256bit password with a 256bit key so that it cannot be bruteforced? Lets say we have an arbitrary but dictionary attackable password that is less than 256bit. (Lets just say the password is '1234Password'). We encrypt this password with a securely random 256bit key ... 1answer 134 views ### AES-128 (CBC) brute force given 90+ rightmost bits of key, known IV and Ciphertext? Given: Known ciphertext (in hex) (ciphertext is the exact length of the message (i.e. non-padded). It is known that the cipher was developed using CBC. There is one and only one ciphertext message ... 0answers 115 views ### Is reverse engineering SHA256-HMAC function possible? [duplicate] Assume HMAC function is used to generate a 6-digt integers time-based onetime password. As follows: $$K_h =\operatorname{HMAC}(k,t) = H((k\oplus\text{opad})\mathbin\| H((k\oplus\text{ipad})\mathbin\|... 0answers 83 views ### Brute force against custom algorithm [closed] In my free time, I write an algorithm for fun (and it may be the best hobby I had so far). Currently, the output this algorithm produces is indistinguishable. I ran multiple analysis process and ... 1answer 181 views ### Finding a secret key corresponding to a public key As far as I know, a secret key corresponding to a given public key is not unique. So, for example, there are actually multiple secret keys that can produce the same digital signature under RSA ... 1answer 137 views ### Time to guess a 100-bit key at one billion operations per second and one billion cores? My math is as follows. If you can do one billion operations per second on a single core, and you have one billion cores available, that translates to 2^{60} operations per second, and 2^{100}/2^{... 1answer 202 views ### XTEA brute force 128 bits key, 64 rounds Is my calculation correct that to bruteforce XTEA with 128 bit key: https://www.wolframalpha.com/input/?i=number+of+4-permutations+of+4,294,967,295+objects Would require that many permutations? Are ... 2answers 3k views ### Why do look up tables speed things up compared to brute force? I'm currently reading up on lookup tables and efficiency. In my uni script it says the following: For Brute Force: Preparation time: O(1) Disk space requirement: O(1) Time required to crack the ... 1answer 143 views ### How to make my hash more robust to the brute force? I'm using PBKDF2 SHA 256 with 100 000 iterations to generate a secret. I want to increase the cost of brute forcing the passphrase I use to generate the secret. I'm thinking of using scrypt after ... 1answer 957 views ### In the RSA DES challenges, how did the contestants know they had found the right key considering they weren't given any plaintext? If the contestants were given both the plaintext and ciphertext, it's straightforward. Just bruteforce all 56-bit keys until you find one that maps the given plaintext to the given ciphertext. But ... 2answers 384 views ### Is a single md5 hash a good way to generate an AES key? This site says how to encrypt data using a password in go using AES-GCM. It says the following: When encrypting and decrypting data, it is important that you are using a 32 character, or 32 byte ... 2answers 453 views ### brute force RSA [closed] I have a ciphertext c_t and a RSA public key pair (e, n). I also know that the encrypted message is a three-letter word in the ... 1answer 292 views ### Comparing DES and DES-X variation: Enc(m) = DES_{k_1}(m \oplus k_2) I came across this question: Test the security of the following variation of DES-X cryptosystem, which uses 2 keys k_1 and k_2:$$Enc(m) = DES_{k_1}(m \oplus k_2)$$(Basically, it uses the 2nd ... 2answers 78 views ### How to ensure confidentiality of an encrypted but public message given that computation power increases? Say I encrypt a message with the public key of a party whom I want to contact with and then send the ciphertext over an insecure channel. Naturally, an adversary who listens to this channel can ... 1answer 167 views ### How long would it take to crack a double hash if salt and final hash are public? I have a hash of a file$H_1$and then I add salt and rehash it:$H_2$. I make my$H_2$and salt public and I use my$H_1$as a password. How long would it take for this to be cracked with someone ... 2answers 77 views ### Is the key safe if attacker know the encrypted and decrypted message? Given an attacker know both the encrypted message (+ an iv) and the equivalent decrypted message, is it possible for him to craft a new encrypted message that could result in a desired decrypted ... 1answer 61 views ### Encryption method that is purposely vulnerable to cracking parts at a time? Is there a method of encryption where your key is made up of$n \cdot s$bits, but also such that an attacker would know when they've successfully cracked each$s\$-bit part? For example, the full key ...
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suppose the password used in the RC4 encryption of a plaintext is an English word of 6 letters that we do not know or forget it . Is it possible to recover it if we only know the ciphertext but not ...
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### Is AES practically unbreakable? [duplicate]

Is AES practically unbreakable? Is brute force attack practical on AES?
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### Benchmark (hash rate) for SHA-3 (SHAKE128)

To estimate the time for brute-force attack we need to compute keyspace size divided by hash rate, where the hash rate (hash/second) varies depending on the computer's capabilities. The website https:...
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### Benchmark for SHA-3 (Shake128) [duplicate]

I am trying to find the average of hash rate (benchmark) for SHA-3(Shake128) for a normal and supercomputer in order to estimate the brute-force attack which I can get if from ( keyspace / hash rate )....
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My question is kinda simple. I want to use AES-256 encryption to encrypt my backup. Using a password like this: ...
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### Hash Function SHA-3 [duplicate]

I would like to discuss the minimum input of hash function to consider strong (e.g Shack128 (SHA-3)). I have a mechanism based on SHA-3, but the input is just 40-bit, some friends told me 40-bit input ...