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Questions tagged [cryptanalysis]

Cryptanalysis is the part of cryptology dedicated to the mathematical analysis of the weaknesses of cryptographic algorithms, the goal being to defeat some of the security properties that the algorithm should fulfill, e.g. decrypting data which has been symmetrically encrypted with substantially less effort than what would be needed to try out all possible keys.

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1answer
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Find seed used in Math.random LCG given a list of outputs [duplicate]

Given one or two sequential Math.random outputs generated with Internet Explorer's linear congruential generator, is it possible to find the seed used in the LCG and find subsequent outputs? Here is ...
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Deciphering ciphertext with an unknown key and algorithm [closed]

How can I get started on understanding how to decipher this ciphertext when I don't know the algorithm or key used? TDcbY xqCa NeAA OsWMirK FNFOm bYRUYAkxl,  tqwl  axZU  XTaLrBSFv OI G vWjBZyqhz.  ...
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1answer
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Will prepending random data (of random length) result in more secure communication?

Many files begin with a "well-known" header sequence which I imagine helps a lot in performing cryptanalysis over a huge number of data transfers. So I have the thought of prepending a block or two ...
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Clarifications regarding testing the cipher using NMAP scan

I'm running the below Nmap command to test the strength of the cipher suites I have used in my host nmap -sV --script ssl-enum-ciphers -p 8673 <host> My server supports TLSv1, TLSv1.1, TLSv1.2 ...
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2answers
294 views

Is there a difference between encryption keys and encryption certificates?

Learning about cryptography. Experimenting with attacking the algorithm it's self. My question regards vocabulary basically. Are encryption keys and certificates the same thing or are they different? ...
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1answer
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Can you find the ransomware key if you already have decrypted files?

Disclaimer: I have very very little experience with ransomware/encryption, so I'm sorry if I ask something stupid. Ransomware attacks are all over the news, especially this year. And this got me ...
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5answers
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SSH - If Eve has the passphrase and public key, can she derive the private key?

I have used ssh-keygen for creating an RSA 4096-bit SSH private and public key pair. I used a passphrase for the private key. If an attacker, Eve, knows the passphrase in addition to the public key: ...
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3answers
407 views

Why is it necessary to minimize redundancy in the ciphertext of a stream cipher?

I am utterly confused about this. I understand why you would want to minimize redundancy if you're using a substitution cipher, but why is this necessary when using a stream cipher such as RC4? ...
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Should we be using SHA3? (2017)

This question is a duplicate, however I feel that it's necessary given the question. The original was posted in 2012: about 5 years ago before NIST had even published the final specification. The ...
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2answers
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Are stronger passwords safe in case of a breach?

Passwords are not generally held by websites, instead, they hold hashes of your passwords. When there's a breach, these hashes are stolen and they are matched against rainbow tables of pre generated ...
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Veracrypt - When using Full OS encryption, isn't it easier to decrypt using the OS file placement?

Let say you encrypt A.jpg and B.jpg , B is just after A in the hard drive. let say A = 0101 B = 1001 on unencrypted HDD : AB = 01011001 once encrypted : AB = 11111011 if someone know A is the ...
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How to determine what type of encoding/encryption has been used here? [duplicate]

Is there a way to find what type of encryption/encoding is being used? For example, I am working on php script they using this encryption to give the output URL to android apk for example this out ...
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1answer
137 views

Where to submit an algorithm for analysis? [duplicate]

I'm developing a cryptographic toolkit and plan to employ custom algorithms for hashing, password stretching, etc. Is there a way I can get them analysed? Yes, I can post it on my website and on sites ...
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1answer
274 views

With a very large number of GUIDs, can one predict the previous and subsequent GUIDs that will be generated?

I've been reading up on GUIDs. According to the Wiki: Cryptanalysis of the WinAPI GUID generator shows that, since the sequence of V4 GUIDs is pseudo-random, given full knowledge of the internal ...
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Simulation vs Formal Analysis of Authentication Protocols

I received a review for my journal paper in which we proposed WOOlim or nspk kind of authentication protocols. We proved the strength of our protocol with rigorous formal methods using CSP and rank ...
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2answers
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Why haven't (most of) the Zodiac Killer's letters been decrypted? [closed]

The Zodiac Killer was a serial killer in the late 60's and early 70's. The twist is, he would frequently taunt the local press with cryptic letters. Four of these letters were actually encoded, but ...
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3answers
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Targeted acoustic keylogging attack prevention

To what level could this be applied to? Could someone record keystrokes on a keyboard and in combination with typing habits start to put together a picture of what the user is typing? If this is ...
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How the NSA can break trillions of encrypted Web and VPN connections

Based on Diffie-Hellman's negotiation of key exchange, why would it turn out that only a few primes are commonly used? What and who determines the prime? Would it not be safer to use a safe prime? (...
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1answer
148 views

Finding the cryptographic hashing algorithm, given the plain text and the corresponding salted hash [duplicate]

I have a salted hash (say about, 110 characters long) and the corresponding plain text that I used for hashing. As the title says, is it possible to do find the algorithm via crypt-analysis? What is ...
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0answers
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What are the formal methods to analyze Authentication Protocol

I designed an authentication protocol for consumer-producer applications, which barrows features from Kerberos and Tesla. To check the strength of protocol I considered different well known attacks ...
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2answers
510 views

Crypt-analysis methods for breaking or finding weakness in an encryption algorithm? [closed]

How cryptanalysts work on an algorithm related to diffusion/confusion factors in order to find a weaknesses in an algorithm, for example how cryptanalysts could find weakness on DES? is there methods ...
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Does it increase the security if we split data to n pieces and encrypt each one with different key and different algorithm?

For example: a 10 MB file will be sliced to 10 pieces (each 1 MB) and then dispersed between network nodes. Each node will encrypt it with its own key and different algorithm (AES, TwoFish, Blowfish, ...
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2answers
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How can an attacker identify the encryption method with only ciphertext?

Assume that attacker only could obtain ciphertext, but knows that method is symmetric. Is there a way to find which algorithm was used for the encrytion? And in general, if attacker knows the ...
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Which parameters can I use to analyse my cipher? [closed]

I have made a new methodology for a symmetric key cryptography in which I have used matrix operations, a boolean function and ASCII conversion. Please suggest me the possible parameters to judge my ...
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1answer
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Tell type of encryption if given both input and output strings [closed]

I have the string Thisisatest that is encoded as MDQ4MGFhMzRhYTNkYjM1OGIzN2NkZTJhYjZiNjUzMjY= and I am trying to find out what encryption is used here. I think that the encoded string is base64 ...
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How is a hash's algorithm detected based on the hash?

I was reading an Ars Technica article this morning and came across the following towards the end (emphasis mine): Equation Group included six other hashes in different exploits that remain unknown ...
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1answer
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Soundness of GRC.com Haystack padding concept [duplicate]

I was wondering how sound is the concept presented by the Gibson Research Corporation (see below if you do not want to follow the link) about simple passwords (= very easy to remember) with the ...
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1answer
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Is there a method to get plain-text from cipher-text in HMAC SHA-1, given that the key is known?

This is technically not even an attack. We have all the resources at hand, except for the original plain-text. We have the cipher-text (to be converted back to plain-text), as well as the key. The ...
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1answer
545 views

Can a botnet be used to effectively break encryption keys?

Can a botnet amass and coordinate enough computing power to break encryption keys that are typically considered to be secure (through brute force)? If this is the case, do we need to make our ...
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1answer
116 views

Calculating the breakability of a given encryption method

I will soon be doing a very important project for school. The main goal of my project is to find a mathematical way to calculate the breakability of a given encryption method of ciphertext. Is there ...
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2answers
2k views

Find DES encryption key having input and encrypted output

Having the source string: S3nh4#1 And the generated encrypted string: csf7259aT07Rw Using this script, it identified the algorithm used to encrypt as DES(Unix) I wonder if it is possible (in ...
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1answer
235 views

How to cryptoanalyze a one time pad that uses a plain text document as the pad?

I have read that in order for a one time pad to be truly secure, the pad itself must be random data. Given the practical difficulty of sharing a secure random pad, I was wondering what would be the ...
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1answer
42 views

Key Extraction via electrical signal processing

Looking for a link to what I believe was recent research that was similar to "RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis" - but instead of being based on acoustic emanations, the ...
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5answers
375 views

Is it ever possible to crack an encryption key character by character?

In movies and TV shows, characters are often depicted using devices and applications that are able to determine an encryption key or passcode character by character (or digit by digit). I am a ...
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2answers
527 views

Crack Unknown Encryption [closed]

I was challenged by a friend to decrypt a piece of text that was somehow encrypted. The encrypted text is the following: LY3IoH5HWSnp9-efCfOH3jqmoGaXdURF4YAKgIh2KotjHLyFbLBgXr0uzPu1-...
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1answer
140 views

What keeps the private key safe if an attacker has both clear and encrypted copies of a message and the public key?

Let's say someone obtained a message in both clear text and in its encrypted copy with asymmetric cryptography, like RSA-2048. He also has the public keys. Is the private key still undiscoverable? ...
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2answers
199 views

Cryptanalysis of encrypted data at rest

Imagine I have a file encrypted using AES CBC mode with a key and a random IV. The attacker access to the encrypted text and the IV used but not the key. In this scenario there is no vulnerability ...
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1answer
759 views

Knowing Input&Output, How to determine encode method and the passkey that was used in encoding?

I've looked on this site and on SE. but I couldn't get a handle on this. Is there a way to find what type of encoding (and/or encode key) is being used? For example, I am testing a web application(PHP)...
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1answer
932 views

Klein and PTW wep attack

I'm working on an implementation of Klein's wep attack. For that, I've set up a router with wep encryption and collected 50,000 unique IVs from it. I tried only calculating K[0], meaning - the first ...
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2answers
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Is AES encryption vulnerable?

I was reading weaknesses in AES encryption. Unfortunately, I have a website that uses AES: Its database is almost entirely AES encrypted. Is there a real threat? Would it be worth to refactor the web ...
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1answer
2k views

Cracking DES(Unix)/MD5 ARP

This is a basic example of an Unix Pass Encryption. I have a little Hash of MD5 ARP: user50:$apr1$w7YNTrjQ$0/71H7ze5o9/jCnKLt0mj0 user60:$apr1$AIw2h09/$Ti0TRlU9mDpCGm5zg.ZDP. I need to find the ...
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1answer
112 views

Frequency Analysis [closed]

I have started looking into Crytography, and the obvious starting point is frequency analysis. As a task for myself I thought it would be good to compile a script which could be used for perform the ...
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2answers
357 views

Do known plaintext attacks lead to exposure of the key?

I say that if a professional code breaker has a bunch of data, the encoded version of said data and the encoding method he can figure out the encoding key. It is just a matter of having enough data. ...
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833 views

Google's usage of RC4

I was reading about Google's usage of RC4 and an answer on stackexchange website stated the following: I know Google uses RC4 for most of its services, and this is the reason one shouldn't keep ...
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5answers
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What kinds of encryption are _not_ breakable via Quantum Computers?

There's the recent article NSA seeks to build quantum computer that could crack most types of encryption. Now I'm not surprised by the NSA trying anything1, but what slightly baffles me is the word "...
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2answers
114 views

Facing hard encryption [closed]

I have a little problem with encryption. I have this cipher text "AA969CF9657F77C597C8EAFF1594D59374E4977F" and i know that correspond to "http://jogos.meo.pt/". I have another samples, but i can´t ...
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2answers
581 views

cold boot attacks

To quote the wikipedia article on Cold Boot Attacks: In cryptography, a cold boot attack (or to a lesser extent, a platform reset attack) is a type of side channel attack in which an attacker with ...
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4answers
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At what point does adding more iterations to PBKDF2 provide no extra security?

If my true passphrase is used only to generate a hash which is used as the cipher's actual key, doesn't that mean it's possible to try and brute force the cipher itself? I know it would take an ...
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2answers
911 views

What is (“ASCII” redundancy) which is said to be required to retrieve the original plain text in 2 times pad?

Sorry for the long title :$ In a video speaking about attacks on the one time pad which uses psudorandom generators (PRG), It's said that Eve can retrieve the plain text of 2 messages that have been ...
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1answer
351 views

Timing analysis attack and cryptosystem

Why is a “Timing Analysis Attack” a problem for a cryptosystem? I've been trying to learn security, and have a question about timing analysis attack.