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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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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 ...
3
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1answer
75 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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0answers
39 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\|...
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0answers
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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
37 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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1answer
116 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
38 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
49 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 ...
5
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1answer
870 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
164 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 ...
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2answers
107 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
83 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 ...
2
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2answers
69 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
76 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
70 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 ...
2
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1answer
56 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
388 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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0answers
36 views

How effectively is hard to brute force an AES key? [duplicate]

I know that AES(Rijndael) algorithm uses a 128 to 256bits key. Using a brute-force attack how many tries are required to have mathematical assurance to find the exact key to decode the message(in case ...
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1answer
142 views

Is AES practically unbreakable? [duplicate]

Is AES practically unbreakable? Is brute force attack practical on AES?
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2answers
350 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
126 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
52 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
98 views

6 Byte for HMAC in wireless system secure?

A wireless system has 8 byte payload and 6 byte for message authentication. Scheme: ...
5
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1answer
503 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
179 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
616 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
87 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
173 views

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: ...
1
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1answer
624 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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0answers
47 views

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
78 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 ...
3
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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
198 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
3k views

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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0answers
62 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
74 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
152 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
81 views

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 ...
1
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1answer
559 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
163 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
117 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
280 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
734 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 '@...
2
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1answer
384 views

Brute-force attacks practical limit

My question is about practical limit for brute force attacks. As I know 3DES with 56 bits key length can be broken via brute force. I also heard the same news about 64 bit key length (correct me if I ...
5
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3answers
563 views

DES Bruteforce attack and false positive keys

I have read that a bruteforce attack (regardless on which block cipher is used) can lead to a false positive if key space is greater than blocks space. It is pretty clear to me that is due the pigeons ...
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0answers
125 views

Triple DES: Does knowing the plaintext limit my keyspace for brute force?

My goal is to try and decrypt a single 8 byte block of a Triple DES encrypted data block and in doing so discovering the 8 byte keys that were used. This is mostly an academic exercise but could ...
2
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2answers
272 views

Is multiple hashings of a cryptographic hash function an acceptable way to increase complexity?

Is nesting/re-hashing a viable way of slowing down a fast cryptographic hash function (such as SHA-256) to slow down brute-forcing attacks on shorter passwords? The use of longer passwords would of ...