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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System for securely authenticating content acquisition

I'm having trouble designing a system for authenticated content from my site distributed by other people. I'm working in Ruby on Rails, but I don't think that at a theoretical level my question isn't ...
0
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2answers
413 views

Algorithm to generate NTLMv2 Hash in PHP

I am trying to develop a PHP function to calculate NTLMv2 hash by providing server & client challenge, domain, account and password. The resulting hash appears to be not correct. Can someone ...
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0answers
218 views

Configure Asterisk for lan with SRTP enabled SipDroid

I want to have a secured call over internet between two android phones. I have found SipDroid which is an open source SIP client for Android. And also I have followed this to install Asterisk, Dahdi ...
10
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3answers
409 views

has scrypt withstood the test of time?

I've always heard that scrypt was better than bcrpyt... because of memory causing GPU a very difficult time to crack. However, the notion always was that scrypt hadn't been tested, it was kind of a ...
6
votes
2answers
1k views

1024-bit DHE vs 2048-bit RSA

Currently with apache/mod_ssl, if DHE is enabled then a 1024-bit ephemeral key will be used. I found the following quote in Adam Langley's blog: Ideally the DH group would match or exceed the RSA ...
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2answers
1k views

Encryption - which are/aren't NSA backdoored [closed]

I prefer bcrypt because it uses a lot of "power" to decrypt. But which encryption can i use that is most likely safe for NSA (which knows a lot of backdoors) and is relatively slow to decrypt. I ...
3
votes
2answers
542 views

Is it safe to expose an SHA1 hash of an encryption key?

Assume that party 1 and party 2 each possess a key used for AES encrypting data. Assume that the key was properly randomly generated and securely passed between them. Now I need a way for party 1 to ...
1
vote
1answer
206 views

How is the FileVault master key protected?

FileVault has the functionality to both allow and disable user accounts from booting up the encrypted drive. Reference: this cnet article. See also the stack exchange question How does FileVault 2 ...
9
votes
2answers
845 views

How does a weakness in a random number generator lead to a compromise of the entire cryptographic process?

In the news, there are several articles (here, here, and the technical point of view) which have to do with a weakness in a random number generator. The question is somewhat twofold. What symptoms do ...
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1answer
120 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.
1
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1answer
292 views

OpenSSL DH modp size

If OpenSSL is configured to use a DH for key exchange, e.g. TLS_DHE_RSA_WITH_AES_128_CBC_SHA, where does it take the size for modp (or even modp itself) from? The following is a screenshot from ...
5
votes
1answer
2k views

What block ciphers and algorithms are now safe? [closed]

I work for a large non-US based international organisation. Regarding the recent leaks about the NSA breaking most encryption on the internet, we now know the US and UK governments are actively ...
5
votes
1answer
242 views

Any not totally insecure browser vulnerable to BEAST?

People still worry about BEAST quite a lot when configuring web servers to the point of preferring RC4 over AES-CBC. But most browsers mitigate BEAST even while using TLS 1.0. Is there a browser ...
0
votes
2answers
925 views

applications of double DES and triple DES

what are the applications of multiple encryptions? where the multiple encryption like double DES and triple DES algorithms are use?
2
votes
2answers
885 views

Explain real world symmetric key encryption

I'm new to cryptography. While reading about symmetric key encryption, it was mentioned that it requires secret key exchange so that 2 parties can decrypt the ciphertext. Now, using some encryption ...
0
votes
3answers
452 views

Protecting data through an XOR operation with sufficiently long keys

Suppose two parties S and D would like to protect a communication channel. Therefore, S and D exchange two sufficiently long key sequences SB und DB of random bits over a secure channel [e.g not over ...
6
votes
1answer
2k views

Consequences of tampered /etc/ssh/moduli

What are the consequences if an attacker is able to modify the /etc/ssh/moduli file?
1
vote
1answer
213 views

Does DUKPT support offline mode?

I have been working on the payment side with RSA and AES encryption which I got a fairly well technical understanding of encrypting credit card details. Recently, We adopted a new chip and pin device ...
23
votes
5answers
3k views

Why is Bruce Schneier recommending symmetric crypto over public key crypto

I just read the article written by Bruce Schneier, the crypto guru. In the article, he says : Prefer symmetric cryptography over public-key cryptography. But, he doesn't shed any light as to ...
3
votes
1answer
239 views

Properly implemented strong crypto systems [closed]

I have read this article about the revelation that in 2010 major encryption mechanisms including big four (hotmail, facebook, google, yahoo) and other encryption mechanisms were broken by NSA and ...
66
votes
3answers
3k views

Did US and UK spy agencies defeat privacy and security on the internet?

This question is meant as a canonical question in regard to the US and UK spy agencies compromising end nodes and encryption between nodes to spy on people they suspect to be terrorists. However, this ...
3
votes
1answer
669 views

Hashing passwords before inserting into database

For the last 2 weeks I have been reading many blogs about website security and hashing passwords. Many sites have mentioned the pro's and cons about different ways of doing this, which has left me a ...
9
votes
2answers
398 views

How do new security and cryptography techniques/protocols avoid the chicken-and-egg problem?

. . .better solutions have been proposed and will be worth considering once they have withstood the test of time (i.e. “5 to 10 years in the field, and not broken yet”). -From Thomas Pornin's ...
10
votes
4answers
661 views

What was SSL 1.0?

What was SSL 1.0? SSL 2.0 and 3.0 are well-known and well-documented. But what did the SSL 1.0 protocol look like? Wikipedia says there was a SSL 1.0 but doesn't say anything about how it worked. ...
0
votes
1answer
190 views

Encrypted data transfer with middle node and asymmetric key

I'm looking forward to pass data from a node A to a node B using asymmetric cryptography, but with one (huge) constraint: When A sends data to B, it is possible that B is offline. I would like to be ...
2
votes
2answers
724 views

Please help verify my understanding of Domain Validation (DV) SSL Certificate

This is what I understand so far from reading various knowledgebase and article about DV SSL. Can anyone please help clarify if any of these is wrong? DV SSL (and SSL certificate in general) is only ...
1
vote
2answers
437 views

Are there any dangers in exposing git sha1 commit hashes?

For a non-public repository, are there any potential security concerns in sharing git commit hashes? For example, when I post a git-related stackoverflow question that involves git commits from ...
3
votes
1answer
133 views

How signature validation would be checked on server side?

Sorry, It may be possible that few things are repeated in my question. I have gone through some documentation/discussion signing an API request and twitter signature documentation As per the ...
6
votes
3answers
640 views

How can I prove that I wrote a certain blog post?

I would like to be able to prove that I wrote the article that resides at a given URL on someone else's blog. Is there a way that I can do this with public key cryptography? I know a bit about the ...
5
votes
2answers
618 views

Designing a cryptographic file-sharing protocol

As a learning project, I am trying to implement a secure way to share files with a friend over dropbox. (I am not looking for existing software, I am doing this in order to learn how to do this ...
4
votes
2answers
592 views

NaCl: US Export Regulations

I'm in charge of a product security in our US based startup and I plan to use NaCl for encryption (well, Sodium, actually). I'm trying to navigate the labyrinth of US export regualtions - something I ...
6
votes
2answers
647 views

How is OTR messaging with Socialist Millionaire Protocol (SMP) protected from Man In The Middle?

So imagine the next situation: Alice wants to initiate OTR instant messaging session with Bob but Joe is Man In The Middle. Alice negotiates a shared secret 'X' with Joe (thinking he is Bob) using ...
0
votes
2answers
395 views

Using a Common Private Key for Digital Signatures

I have a mobile application and a server. The mobile application communicates with the server through a web services framework via SSL. The mobile application allows customers to pay for ...
3
votes
2answers
423 views

Crypto Browser add-on

What are the known limitations with browser addon/extensions that do in browser encryption vs a native implementation in the browser. The addon would expose cryptographic primitives for use in ...
1
vote
1answer
477 views

Is server-side cryptography with user-only access possible for email services?

I came across the Lavabit High Scalability Writeup and got curious. Do you use any particularly cool technologies or algorithms? The way we encrypt messages before storing them is relatively ...
1
vote
1answer
4k views

Create RSA public, private key pair having numbers generated already

I want to know to to generate working RSA key pair, with correct syntax. Let's say i have already generated somehow my numbers for 512bit key, which are: e = 00065537 d = ...
0
votes
2answers
266 views

An attempt to overcome the key distribution problem inherent in one time pad cryptography

After reading about the 'imminent cryptocalypse' etc, I started thinking about a cryptographic protocol that would not depend on complexity of mathematical operations (e.g. factorisation, discrete ...
1
vote
2answers
445 views

Is it possible to respect a user's privacy while collecting phone MAC addresses?

In London, there are trash bins that track a phone's MAC address and monitor the users movement from one location to another. I want to see if there is any best practice for collecting private ...
6
votes
2answers
364 views

Salt placement prior to one-way hash

In one-way hashing its common to prepend or append the salt to the secret and then hash it: (salt + secret) or (secret + salt). I was thinking of this metaphor as salt falling on a plate of food. It ...
0
votes
2answers
429 views

Is there a way to configure WPA2-PSK to provide Forward Secrecy?

Is there a way to secure an wireless connection against a decryption attack where the PSK is known (E.G. Airdecap-NG)? Is it possible to configure Forward Secrecy on 802.11 Wireless Connections?
5
votes
1answer
309 views

AV boot disks and Truecrypt encrypted drives

I was wondering if there were any "how-to" guides on what is needed to modify AV boot disks, such as Sophos, kaspersky, AVG etc in order to load the decryption drivers/bootloader for Truecrypt before ...
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votes
1answer
139 views

Posting public key [closed]

Should I put my public key on my website so that people can securely contact me. I have seen personal sites where there public key is at the bottom of the page such as this site by the computer ...
6
votes
1answer
849 views

Is it safe to use rng-tools on a virtual machine?

I am currently working on an app that needs to create GPG key pairs using the gpg tool. Unfortunately, this tool takes a long time to generate a key pair if there is insufficient entropy/randomness ...
1
vote
1answer
133 views

Software library for 1-2 oblivious transfer?

I'm looking for software libraries that support 1-2 oblivious transfer of a single bit between two parties. Googling seems to bring up lecture notes, explanations, and research papers but not ...
4
votes
1answer
844 views

Whats the best custom compression method to use when I have SSL?

Suppose I have an application which does encryption using SSL and provided you cannot control what cipher suite is being negotiated, and assuming that I have some custom compression over the data ...
8
votes
1answer
645 views

How to get a 'million rounds of PKCS#8 + PBKDF2' with OpenSSL?

I posted this question Is a passphrase-protected SSH private key susceptible to a dictionary attack? a few days back. An excerpt from the final answer: With PKCS#8 + PBKDF2 and one million ...
11
votes
1answer
12k views

Secure Configuration of Ciphers/MACs/Kex available in SSH

Following on the heels of the previously posted question here, Taxonomy of Ciphers/MACs/Kex available in SSH?, I need some help to obtain the following design goals: Disable any 96-bit HMAC ...
5
votes
2answers
822 views

What's the modp length of diffie-hellman-group-exchange-sha256?

OpenSSH 6.2 offers the following key exchange algorithms by default ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 diffie-hellman-group-exchange-sha256 diffie-hellman-group-exchange-sha1 ...
4
votes
2answers
885 views

Rounds of MD5 and SHA512 Hashing Algorithms

What is the exact number of rounds employed by the MD5 and SHA512 hashing algorithms? According to various sources, the SHA512 hashing algorithm employs a total of 80 rounds ...
3
votes
2answers
360 views

Should I customize my Root CA's thumbprint/fingerprint? (SHA1 or MD5)

My goal is to make a certificate's thumbprint "easier" to verify, and not reduce security in doing so. Given that the RSA-based Bitcoin technology has a concept called a "Vanity address" where the ...