Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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3answers
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Key Exchange using PKI

I'm new to the field of cryptography and trying out a sample program to understand PKI key exchange mechanism. I tried creating a self signed certificate using openssl openssl req -x509 -nodes ...
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1answer
1k views

What would be the scenario if P = NP for RSA algorithm?

Suppose I am using RSA for my security system. Now someone discovers find a polynomial time algorithm for RSA. Then what measure should one that such that RSA never breaks. Maybe large number of used ...
7
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2answers
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When using symmetric key encryption, do we need to sign?

Say we're using a shared key between two parties, that has been distributed using public key encryption, is it still necessary to sign any data that's encrypted using the shared key? Or is it enough ...
2
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2answers
1k 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 ...
8
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1answer
690 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 ...
10
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2answers
870 views

In the recent DKIM vulnerability, how did someone determine key length by looking at headers?

Having read this recent article : Wired-DKIM vulnerability, I have a couple of questions. How can one determine the key length that is being used simply by looking at the headers ? And I'm assuming ...
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2answers
464 views

How do I construct a rainbow table to crack a 6 character password? [closed]

Given the hash: 491c290affbf5436f0fc0584ccefb2 how do I construct a rainbow table to crack this password?
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2answers
2k views

Are there really functioning quantum computers?

I saw this video on youtube on quantum computing. It says that a company called dwavesys has already made commercially available quantum computer. I checked on the website and it exists. I thought ...
7
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3answers
653 views

A safe license System

So I'm trying to think of a good way to check if the license key a user supplies for a program is legit or not. Let's suppose this is the way they get there license They make some type of purchase. ...
4
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3answers
2k views

rsa encrypted hash == rsa signature

$ echo -n "1327943823" > test_ok.txt $ openssl dgst -sha1 -binary -out test_ok.sha1 test_ok.txt $ echo "GURbsl4CFPCG83RCZxsEpoRleXicXQhH1OC4Fk77b7EMj2g8aHUhD/L+sm ...
2
votes
1answer
275 views

Seeding GPG keygen with a hashed secret [duplicate]

Possible Duplicate: Tool for public key cryptography where password is the private key? I was wondering if you guys could clue me in to potential problems with using a hashed password as ...
6
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3answers
337 views

How much added security do I really get with a longer key size?

Imagine I have a cipher which supports keys of 128, 192 or 256 bits. Suppose that there are no vulnerabilities in the cipher regardless of key length. I'm going to use it to encrypt something, and ...
0
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1answer
143 views

How to initiate the learning process of modern day IT Security concepts mainly cryptography? [closed]

I am a programmer with about 7 years of experience mainly in Java . I am interested in the subject of cryptography very much . I love algorithms and datastructures . When I first started learning ...
2
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2answers
1k views

Revoked certificate validation using past times

I'm working on XAdES implementation for Java, as such I require cryptographic implementation to be able to verify certificates in the past. Unfortunately I have problems verifying revoked ...
4
votes
2answers
933 views

Block cipher Implementation in C++

I'm writing an implementation of a block cipher in C++. I would like to study differential cryptanalysis of the cipher, so I'm generating random plaintexts and keys and then encrypt them. Which is ...
1
vote
0answers
305 views

Verifying Authenticode signed executables and DLLs using OpenSSL API [closed]

I have installed openssl and now the rsa_test.c is running fine. What I want to do is: Open any exe or dll digital certificate. Extract the Thumbprint and PublicKey. The public key contains the ...
5
votes
1answer
353 views

security issue on storing keys and certificate on token

I'm creating a sample USB token with Atmega64. As I have to store both the public and private key and the certificate on my token is there any important security issue that I should worry about, ...
3
votes
2answers
767 views

Distributed XAdES-X and XAdES-A signatures over multiple documents

As the standard is not completely clear in this matter, I'm trying to found out if the XAdES standard (ETSI TS 101 903 v1.4.2) describes distributed case in which the SigAndRefsTimeStamp element or ...
3
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4answers
6k views

What Are The Best Practices (Application Security Policy) For Modifying Rijndael Salt, IV, Pass Phrase

(Note: originally posted in SO - advised to post on SSE) With regards to Rijndael encryption, what (if any) are the best practices (and consequences) regarding the periodic modification of one or ...
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5answers
1k views

create a variants of MD5

I have also asked similar q here : To create a variants of MD5, I made following changes : MD5 uses a non-linear sin(i)* pow(2,32) ----> i plane to use cos(i)*pow(2,32) Instead ...
2
votes
2answers
1k views

encryption method against man in the middle attack

Let's say there are 3 computers: Alice, Bob, Carol. Carol is network provider, so everything from Alice to Bob and vice versa passes through Carol. Carol can modify messages between Alice and Bob. Is ...
8
votes
2answers
2k views

Should we start using SHA-3? [duplicate]

Possible Duplicate: What is SHA-3 and why did we change it? SHA-3 has been finalized! So, what does secuirty.se think about the new hash funciton? Should we start replacing all uses of ...
3
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2answers
3k views

Using Elliptic Curve Cryptography

I am wondering if ECC could be used the way that the data is encrypted with the public key instead of the random generated key. Is there any advantage doing that comparing to the "traditional" way of ...
11
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4answers
3k views

Tool for public key cryptography where password is the private key?

Is there any free & open source tool for public key cryptography, where the private key is just a chosen password? Here is what I need: I want to make backups every hour using a script I want ...
4
votes
2answers
5k views

Shared Secret, is it a public key or a private key?

Reading the Diffie-Hellman non mathematical explanation i found that some mathematical operations are performed on private-key and the recipient's public key to generate a "shared secret" on both ends ...
15
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1answer
906 views

XKCD #936: under what assumptions is 1000 guesses/second over a network plausible?

In XKCD #936, a rate of 1000 password guesses/second is proposed as a "plausible attack on a weak remote web service". Under what assumptions is this rate plausible? It seems much too high to me. I ...
3
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1answer
315 views

What are the benefits of federated identity management over bare bones public key encryption?

What are the main reasons for having a federated identity system such as OpenID over having identities based purely on a public key? OpenID uses an Identity Provider to confirm that a user owns a ...
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votes
3answers
689 views

find password and iv of an encoded string knowing the decoded string

If I would know the clear and encoded versions of a string could I somehow find the password and.or iv that wore used to encode it? Encoding done with open_ssl aes-128-cbc.
13
votes
1answer
12k views

Where is the salt on the OpenSSL AES encryption?

I'm interested in knowing how and where OpenSSL inserts the generated salt on an AES encrypted data. Why? Im encrypting data in Java classes and need to guarantee that I can use OpenSSL to decrypt ...
4
votes
1answer
209 views

Computational Feasibility of finding 'Good Links' of the following format

I recently stumbled upon this and am checking here to see if what I am proposing is indeed feasible and can be considered a breach of privacy. For obvious reasons I am not revealing the website ...
4
votes
2answers
4k views

Best practices for TrueCrypt + Yubikey combination

I'm trying to find a secure and convenient way to encrypt my external disk with TrueCrypt. Currently I use a 50 character strong password but I'm tired of typing it every single time. I have a Yubikey ...
5
votes
1answer
88 views

Standards for CA cert revocation and time-constrained cryptographic algorithm parameters

I'm working on software that will be in use for foreseeable future (15 years+) that will need to validate XAdES-A signatures (long term archival, similar to PAdES-A, but for XML). That means, it will ...
22
votes
4answers
3k views

NSA Suite A Cryptography: Security through obscurity?

What is the opinion of scholars, cryptographers on NSA Suite A? Containing unpublished algorithms. Could it really be that much better than the published algorithms besides being obscure and not ...
4
votes
2answers
528 views

Why is Elliptic Curve Cryptography not used much outside of government? [closed]

It seems that Elliptic Curve Cryptography, being required by the US government, is not being used outside of the government. Why is this? And why does the government support it's use for government? ...
22
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2answers
4k views

Is HTTP compression safe?

The CRIME attack taught us that using compression can endanger confidentiality. In particular, it is dangerous to concatenate attacker-supplied data with sensitive secret data and then compress and ...
3
votes
1answer
267 views

CMC (RFC 5272) compatible CA server

I need a CA server or any tool that supports Certificate Management over CMS (CMC) format, described in RFC 5272 (RFC 2797). I need a possibility to generate different Full PKI requests and responses ...
0
votes
1answer
350 views

How key_derivation and key_verification functions are implemented of a 7-zip archive's encryption mechanism?

I am curious about how password recovery works for password protected files. And I want to know the exact flow of the 7-zip encryption mechanism :) !! 7-zip uses the AES-256 encryption algorithm in ...
1
vote
1answer
313 views

Can I combine two of SHA-3 candidates cryptography hash functions and obtain more secure Algorithm? [duplicate]

Possible Duplicate: Are different hash algorithms ever used together? For example, Is possible to combine (Concatenate or Chain or XOR) Skein SHA-3 candidate with Grostl SHA-3 candidate to ...
3
votes
2answers
706 views

What risk does commoditized dedicated SHA256 processors pose to IT Operations?

With the advent of GPU-based computing, and now commoditized/dedicated SHA256 processors, what risk does this hardware pose to cryptography? What security algorithms should be closely watched or ...
2
votes
2answers
2k views

Diffie-Hellman key-exchange: securing prime and base

As we know DH algorithm based upon 2 large prime numbers, which are used to be called as prime and base I am writing app which implements DH key exchange algorithm. From security point of view should ...
12
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2answers
4k 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 ...
18
votes
4answers
7k views

Generate cryptographically strong pseudorandom numbers in Javascript?

Is there any good way to generate cryptographically strong pseudorandom (or true random) numbers in Javascript? The crucial requirement: if a.com's Javascript generates some random numbers, no one ...
6
votes
1answer
6k views

Is PBKDF2 only SHA1 in C#?

I can't find a way of specifying the hashing algorithm used by the PBKDF2 (the Rfc2898DeriveBytes class) implementation in C# System.Security.Cryptography. It seems to be just SHA1. Am I missing ...
26
votes
1answer
20k views

How should API keys be generated?

I want to make sure requests can't be forged and sent on to my server. In order to do this I need to generate an API key per user on my system. The purpose of the key will be to sign requests on the ...
3
votes
1answer
104 views

SSL Based Denial of Services due to Message Digest

On a very high level, its known that SSL/TLS uses message digests to verify the integrity of the messages sent. However, the question I have in mind is : How does SSL ensure a DoS does not happen ...
49
votes
3answers
109k views

Is SHA1 better than md5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than md5 for hashing since md5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
3
votes
2answers
439 views

Distributed md5 crack software?

I'm studying about cracking password using brute force, and in my way I found softwares like John the Ripper and MDCrack, that works really nice, but are restricted to one machine. There is some ...
4
votes
4answers
1k views

Is asymmetric encryption ever recommended for long-term storage?

Is asymmetric encryption ever recommended for long-term storage of data, is it advisable for example to store data in a database such that: 1) A user enters data on a website, it is encrypted using a ...
4
votes
2answers
478 views

From password to key

Can you explain this passage from Wikipedia? When a password (or passphrase) is used as an encryption key, well-designed cryptosystems first run it through a key derivation function which adds a ...
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6answers
3k views

How do RSA fingerprints protect from MITM attacks?

I understand that RSA fingerprints are used to verify that you are really connecting directly to who you want to connect to, and not someone else posing as that site. Like when you do a git push, it ...