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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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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 ...
4
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1answer
45 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 $H^k(P)$ ...
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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? ...
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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.
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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 . ...
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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 ...
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1answer
93 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 ...
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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\|...
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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 ...
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1answer
48 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 ...
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122 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^{...
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1answer
53 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 ...
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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 ...
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1answer
52 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 ...
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1answer
875 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 ...
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2answers
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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 ...
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2answers
164 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 ...
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1answer
113 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 ...
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2answers
72 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 ...
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1answer
99 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 ...
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2answers
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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 ...
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1answer
57 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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1answer
1k views

RC4 password recovery

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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1answer
169 views

Is AES practically unbreakable? [duplicate]

Is AES practically unbreakable? Is brute force attack practical on AES?
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2answers
441 views

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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1answer
138 views

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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0answers
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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 ...
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2answers
55 views

Does applying resources improve time?

A password hash function is applied 12 times to secure a password. If it takes 21 minutes to brute force one application of the hash with the available resources, how long will it take to brute force ...
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1answer
111 views

6 Byte for HMAC in wireless system secure?

A wireless system has 8 byte payload and 6 byte for message authentication. Scheme: ...
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1answer
542 views

Are ciphertext-only attacks on LFSRs possible?

Reading about LFSR, I know that breaking an LFSR by knowing it's design and having enough (plaintext, ciphertext) pairs is an relatively easy task but let's assume we know the design of LFSR and a ...
4
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1answer
224 views

How was this Mersenne Twister seed for a 20-character string known a priori found?

Someone generated a seed for the Mersenne Twister, with the intent of that seed producing this string: "9!dlroW ,olleH"ck,@ Which is 20 characters long. Why he ...
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2answers
813 views

Attack RSA knowing the public key and brute forcing all possible message

Alice want to send a message $m$ to Bob, and encrypt it with Bob public key $K_B$. $A \rightarrow B : \{m\}K_B$ Lets assume I have intercepted $\{m\}K_B$, I know $K_B$ and I know that $m \in D$ (...
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2answers
88 views

Brute force encryption keys base on their length

I need to clarify if my understanding is correct. if I am using 4.2 GHz CPU -one core only- that means: 4.2 billions hertz = 4.2 billion operations per second. (about 2^32) So: 32 bit key : 2^32 \ ...
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0answers
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Decrypt an tex file encrypted with rand() [closed]

Link to encrypted tex file: https://drive.google.com/open?id=1gZCujDYmEL-FZ5o_xBUS-Ng5979HSsZ7 This is my attempt at solving the problem: ...
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1answer
769 views

How to encrypt a short plain text?

I want to encrypt a short plain text (i.e., 30bit), and the requirement is that length of cipher text is the same as the short plain text. It seems that stream encryption methods like CFB-8 ...
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Can anyone recommend a fast to encrypt, slow to decrypt, asymmetric non-secret key cipher?

Let me explain; I'm looking for a cipher that does not have a shared or secret key in the usual sense. In other words, any ciphertext can be decoded by anyone - providing they are prepared to ...
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1answer
88 views

Cryptanalysis - Brute force

Are there encryption algorithms based on transcendental numbers? Is it just theoretical or are they implemented in practice? If so, how useful is brute force attacks against them? (My understanding of ...
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1answer
914 views

If a key is used to encrypt that same key, is the computational cost to brute force it decreased?

If a key d is used to encrypt a message m that is identical to the key d, resulting in a cipher c c = encrypt(m, d) = encrypt(d, d) is the computational cost to brute force d lower than if the key d ...
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1answer
217 views

The strength of ECDH public keys with small order

I am trying to get my head around the methods involved in ECDH and am confused by the public keys that are used. Alice picks a random number A from 1 to P - 1 and then computes A⋅g (g being the ...
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3answers
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Why does Birthday attack work only with random messages and not with chosen messages?

Considering unkeyed hashing functions, I studied that the birthday attack can only work generating random messages and not with messages chosen from the attacker, but I didn't understand why. For ...
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71 views

Are 80-bit keys considered secure as of late-2017? [duplicate]

I've seen a lot of ciphers with variants that use 80-bit keys, like Grain, Trivium, KLEIN, KATAN & KTANTAN, Piccolo, PRESENT, RC4, Skipjack, and TWINE. Some of these designs are younger than six ...
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1answer
86 views

what is the minimum number of keys one would probably use in his brute force attack?

what is the minimum number of keys one would probably use in his brute force attack, Given info- The Algorithm uses a blocking technique where the ciphertext from one block becomes the key to the next ...
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1answer
173 views

weakness of a DES enhancement

The following key enhancement to DES was proposed in order to increase the complexity of finding the keys by exhaustive search. $$\text{DES}^V_{k,k_1}(M)=\text{DES}_k(M)\oplus k_1$$ where the keys’ ...
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2answers
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Is there an advantage to “weak” hashing and stretching over strong hashing?

Is there any sort of practical advantage to using a stretching algorithm such as PBKDF2 on say SHA256 over a straight SHA512 hash? If the purpose of key stretching is to increase the length and ...
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1answer
593 views

How difficult is it to crack sha256(sha256(pin)) with a 6 digit pin and no salt?

My friend forgot the password to his electrum wallet but knows that it's a 6 digit pin. I looked into it and from what I can find electrum uses the sha256(sha256(pin)) to generate the key used to ...
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2answers
190 views

Can a hash of the original plain text file be used to brute force an encrypted copy?

I have encrypted files stored on a public cloud, in the same directory on the cloud I have the sha256 hash of the files before they were encrypted in a text file. The keys used to encrypt the files ...
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1answer
118 views

Exercise: recognizing Hawaiian plaintext

I was given the following exercise to solve: The Hawaiian language consists of 12 letters. There are 7 consonants: HKLMNP and W and there are five vowels: AEIO and U. In a word, no two consecutive ...
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1answer
311 views

How many time does a SHA-1 computation require on modern CPU/GPU? [closed]

I am considering how long a SHA-1 computation will need on modern CPU/GPU's. Just in case we are interested in brute forcing and consider the birthday paradoxon, then we need consider the SHA-1 output ...
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3answers
792 views

How confident can we be that nobody will crack a 128-bit key?

In a context involving a block cipher like AES-128, excluding quantum computers, cryptanalytic breakthrough on AES and implementation attacks (poor TRNG, DPA..), and wrench, how confident can we be ...
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1answer
4k views

Decoding an MD5 hash where I already know most of the string [closed]

Let's say my friend has made an md5 hash of an email address and sent it to me. The email address will be something like 'jessica_XXXX@gmail.com', and I know it begins with 'jessica_' and ends with '@...