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 ...

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74
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8answers
7k views

How would one crack a weak but unknown encryption protocol?

I was reading this interesting question: Is my developer's home-brew password security right or wrong, and why? It shows a weak home-brew algorithm developed by "Dave", and the answers discuss ...
43
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8answers
102k views

How to determine what type of encoding/encryption has been used?

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 encryption/encoding is being used? For example, I am testing a web application which ...
42
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3answers
3k views

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 ...
30
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2answers
33k views

How to estimate the time needed to crack RSA encryption?

How to estimate the time needed to crack RSA encryption? I mean the time needed to crack Rsa encryption with key length of 1024, 2048, 3072, 4096, 5120, 6144, 5120, 7168, 8192, 9216, 10240, 11264, ...
26
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8answers
2k views

If someone breaks encryption, how do they know they're successful?

Let's say I have a file containing a random bunch of bits and then I encrypt it using some modern algorithm (Blowfish, AES, or whatever). If someone captures the file and mounts a brute force attack ...
23
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5answers
16k views

Should RSA public exponent be only in {3, 5, 17, 257 or 65537} due to security considerations?

In my project I'm using the value of public exponent of 4451h. I thought it's safe and ok until I started to use one commercial RSA encryption library. If I use this exponent with this library, it ...
23
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7answers
11k views

Where can I learn cryptography/cryptanalysis the hard way, without going to school ? Any good book?

I'm not so bad at mathematics: I know what are p-list and p-combinations, I know matrix algebra, I know what a XOR is, I know how to tell if number is a prime, etc: I'm not the programmer who hates ...
18
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3answers
3k views

MySQL OLD_PASSWORD cryptanalysis?

The password hash used for MySQL passwords prior to version 4.1 (now called OLD_PASSWORD()) seems like a very simple ad-hoc hash, without salts or iteration counts. See e.g an implementation in ...
18
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1answer
1k views

WPA significantly less secure than WPA2?

I understand at least theoretically WPA2 is more secure than WPA, but in practice does it make any difference which one you use? From what I know there are no known attacks for either except for ...
13
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2answers
3k views

Cracking a linear congruential generator

I was recently listening to the security now podcast, and they mentioned in passing that the linear congrunential generator (LCG) is trivial to crack. I use the LCG in a first year stats computing ...
13
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3answers
1k views

What's the mathematical model behind the security claims of symmetric ciphers and digest algorithms?

Why can SHA-1 be considered a secure hash function? That's something I still wonder about. I understand the concepts of why modern asymmetric algorithms are deemed to be secure. They are founded on ...
12
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2answers
569 views

Is a large number of RSA-encrypted files a vulnerability?

Would having a large number (10^4) of RSA encrypted files make it easier for an attacker to find my private RSA key? Update: These files would be available to the attacker, and perhaps the content of ...
12
votes
2answers
490 views

Correct way to get a number from 0-9 from a random byte?

If I have a good random number generator that gives me a byte of data at a time, and I want to extract a random decimal digit of 0 to 9 from that byte stream, what is the correct way to do that? At ...
9
votes
5answers
678 views

When brute-forcing DES, does knowing something about the plaintext help?

Data Encryption Standard (Wikipedia) I know that with brute force there are 2^56 possible keys to check (56 bits, each either a 1 or 0). But let's say I know the message itself is only made up of ...
9
votes
3answers
844 views

Length of CSRF Token

Is there any standard length of the token which should be used while generating the random tokens? Should we use the same standard which we use for generating Session IDs?
9
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2answers
2k views

Estimating the size of a rainbow table

What are rainbow tables and how are they used? Gives a very precise answer about what rainbow tables are and how they are used. I had always confused hash-tables and rainbow tables. My question is ...
8
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3answers
1k views

time to crack file-encryption password - more than just iteration

I have often seen that takes x amount of time to crack a certain length password. But this just seems to be the amount of time it takes to iterate through all the possibilities. What about the time it ...
8
votes
4answers
537 views

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 ...
8
votes
6answers
808 views

Does repeating one word to form a password result in a similar pattern in its encrypted format?

If i use a single word to form a password by repeating it like the examples below: securesecuresecuresecuresecuresecure SeCuReSeCuReSeCuReSeCuReSeCuReSeCuReSeCuRe ...
7
votes
2answers
1k views

Classical Cryptography Tools

I'm wondering if there are any tools out there that can assist in solving classical cipher text. I'm looking into developing some tools such as frequency analysis, transposition tools and so on but ...
6
votes
7answers
600 views

How easy is it to find a password in a huge text file?

Say that my password is PASSWORD1 I have a 10MB jumbled text file. I hide my password in two parts in the text, between > and < so I can find it myself. Then I put the 2 parts together and add the ...
6
votes
2answers
441 views

NSA crypto Suite B - historical

I'm looking for information on what NSA suggested for use in commercial systems in past times. 90's and early 2000's. I'm mainly interested in PKI and symmetric cyphers for SSL and file/disk ...
6
votes
2answers
6k views

The new CCMP attack against WPA/WPA2 PSK

The use of Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) for WPA/WPA2 PSK is being attacked. This is a trivial attack (offline brute force) against the initial ...
6
votes
1answer
335 views

Identifying, analyzing, and predicting weak session cookies

To elaborate on this, I'm looking at this from the perspective of a hacker/penetration tester. Many times I have seen web applications that I know have weak cookies. I can tell this because I can ...
5
votes
1answer
348 views

Known plaintext; What cipher is being used here? [closed]

plaintext: CANDY VERY CRANBERRY ciphertext: TXOtWjYhVk 8&O$4AmSA plaintext: http ciphertext: cZf. plaintext: http ciphertext: r5Hz This is definitely somehow decodable from ...
5
votes
2answers
558 views

Zero padding in HMAC

Section 2 of RFC 2104 defines the key used in HMAC should be padded with zero bytes up to the block length of the underlying hash algorithm. Isn't this a potential security vulnerability since any key ...
5
votes
1answer
286 views

How valid is the concern over narrow pipe hash function designs?

Narrow pipe hash function designs have recently come under fire, particularly in reference to some SHA-3 candidates. Is this criticism valid? Can it be explained more simply than this paper does? I'm ...
4
votes
2answers
4k views

Is it possible to decrypt a SSL/TLS session without doing a MITM-attack?

I'm not talking about decrypting the connection while the SSL/TLS is happening (MITM) but after the connection is closed and I have a pcap file of the entire negotiation/data transfer process. How ...
4
votes
4answers
4k views

Brute force vs other methods of recovering passwords from shadow file

Do you know any good approach for de-hashing/actually bruteforcing hashed passwords in the shadow file? On various operating systems, any good solutions/methods/programs. Or is it better to upload ...
4
votes
3answers
3k views

Vigenere Cipher - help with decryption (by hand)

So this is a Vigenere cipher-text EORLL TQFDI HOEZF CHBQN IFGGQ MBVXM SIMGK NCCSV WSXYD VTLQS BVBMJ YRTXO JCNXH THWOD FTDCC RMHEH SNXVY FLSXT ICNXM GUMET HMTUR PENSU TZHMV LODGN MINKA DTLOG HEVNI ...
4
votes
2answers
477 views

How can i calculate the number of possible passwords?

I have found a flaw in a site where the password reset feature resets passwords in the following format UpperCaseLetter-Number-LowerCaseLetter-Number-LowerCaseLetter-Number-UpperCaseLetter ...
4
votes
3answers
403 views

Hashed passwords - How many variations of rainbow tables?

First off...I passed the CISSP exam. WOOOO. I had to get that out. GCIH and CEH by Sept. 11' So, while studying for the technical side of things, I see that there are rainbow tables. They are ...
3
votes
2answers
562 views

Can key files be brute-forced like passwords?

Let's say you use a program like Truecrypt or Keepass which allows you to have a password + key file. I understand that passwords can be brute-forced/dictionary-attacked but is the same true for key ...
3
votes
1answer
160 views

Does knowing encrypted information make it easier to find an unknown key?

I'm curious if knowing the exact content of an encrypted message or several messages makes it theoretically any easier to discover the encryption key. Does this speed up a brute force attack in any ...
3
votes
2answers
246 views

is it easier to get the original password if you have multiple hashes of it?

Most users tipically use the same password for multiple applications. Let's say all of these applications hash the password in some way. Would it be easier for an attacker to get the original password ...
3
votes
2answers
220 views

Remedy for not having filled the disk with random data?

Filling a large HDD with /dev/urandom prior to encryption can be extremely slow (even with netcat, multiple instances in parallel, etc) and for this reason I'm sure a lot of users skip this advice ...
3
votes
2answers
1k views

How does a brute force attack actually determine it has succeeded? [duplicate]

Possible Duplicate: If someone breaks encryption, how do they know they're successful? First off, this is not about cracking hashed passwords. I know that a brute-force or dictionary ...
3
votes
3answers
372 views

How to optimize compressed file cracking?

I'm currently doing research on cracking encrypted, compressed files (specifically: uif, zip, 7z, dmg). Looking at all the utilities out there, it seems the time it takes to crack something is ...
3
votes
1answer
181 views

Cracking DES(Unix)/MD5 ARP

This is a basic exemple of Unix Pass Encryption. I have little Hash of MD5 ARP : user50:$apr1$w7YNTrjQ$0/71H7ze5o9/jCnKLt0mj0 user60:$apr1$AIw2h09/$Ti0TRlU9mDpCGm5zg.ZDP. I need to find the pass ...
3
votes
1answer
214 views

What is encryption method for the 3rd part of the Kryptos text?

http://fr.wikipedia.org/wiki/Kryptos_%28sculpture%29 http://en.wikipedia.org/wiki/Kryptos I read the Kryptos wikipedia page, is says it's crypted with a "modular transposition of lines and columns". ...
3
votes
0answers
281 views

Can an attacker guess my password length from a hash? [duplicate]

Possible Duplicate: Possible to detect password length from hash? Is doubling your password adds more security? Considering I do not provide him any personal information relating to it, are ...
2
votes
3answers
586 views

Are the encryptions “broken” with great computing power?

http://www.dwavesys.com/en/pressreleases.html#lm_2011 Lockheed Martin Corporation (NYSE: LMT) has entered into an agreement to purchase a quantum computing system from D-Wave Systems Inc. I'm ...
2
votes
3answers
1k views

what is the fastest and cheapest way to crack this kind of hash - md5(md5($password) + salt))?

I'm looking for a program that can use any GPU (ATI\NVIDIA) and can brute force a vBulletin hash - md5(md5($password) + salt)). I have the salt and hash. the password contains the symbols - ...
2
votes
2answers
731 views

How to test security of an encryption algorithm?

What are the standards methods to test the quality of an encryption algorithms. Secondly if i am trying to implement an encryption algorithm then what practices should i adopt?
2
votes
2answers
579 views

Determine encoding/hashing methods used based on knowing the input and output only?

If I know the initial value of a string and the resulting hash but have no access to the system that produces the output, how can I determine what has actually occurred so I can reproduce the hashing ...
2
votes
2answers
460 views

GOST cipher test vectors

Does anyone know where to find test vectors for the GOST cipher? I have been looking around for quite some time, and have been unable to find anything. I know that the sboxes are dependent on the ...
2
votes
1answer
203 views

Legality and ethics of cryptanalysis on password hashes

I'm working on my dissertation concerning cryptanalysis on password hashes. I'd like to delve into the legal and ethical aspects of cryptanalysis, however, seeing as I'n not at all well versed in law ...
1
vote
2answers
202 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 ...
1
vote
1answer
174 views

Stripping / appending characters from user password before hashing to conceal it forever?

I had this idea to permanently conceal user password by requiring minimum length then stripping certain characters. For example if the user password is secret123, the system will strip it down to ...
1
vote
2answers
806 views

How effective have statistical methods been at breaking encryption?

If we look at how statistical engines run on-line translators, and how they are built, we see that they look at a new language and run a statistical model over it searching for what's probably the ...