Tagged Questions

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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2
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2answers
529 views

How to generate cryptographically strong pseudorandom data very rapidly?

What's the best way to go about generating a fast stream of cryptographically strong pseudorandom data without installing uncommon packages? Drawing from /dev/urandom is far too slow. I had an idea ...
8
votes
4answers
686 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 ...
6
votes
1answer
869 views

Crypter Anti-Virus Test

I have written a very simple/basic crypter in C++ and I would like to test it. How would I go about writing a simple MessageBox program that is "tainted" so that my Anti-virus will attempt to ...
1
vote
1answer
334 views

Don't use encryption without message authentication

The text is taken from the famous answer: Lessons learned and misconceptions regarding encryption and cryptology: Don't use encryption without message authentication Alternatively, you can apply ...
0
votes
1answer
185 views

At what point is a cryptosystem “rolling your own”? [duplicate]

Everybody knows making your own cipher really sucks. Everybody also knows using existing cryptosystems, such as TLS, totally doesn't suck. But when is the line drawn? For example, would I be rolling ...
1
vote
1answer
1k views

How is the HMAC key exchanged?

Just wondering about this. Does it need a PKI to work?
2
votes
1answer
567 views

Is there any functional distributed timestamp server available? If not what about this homebrew solution?

Objective A secure Arrow of Time with unpredictable future behaviour to stop attackers or DDoS BotNets from pre-calculating proof-of-work and other gateway protections for P2P/F2F. A distributed ...
3
votes
1answer
150 views

S/Key as an alternative to UNIX passwords

There is this password system called S/Key I saw on the Internet. Can someone give me a brief description about S/Key and how it works? Can S/Key be an alternative solution to the UNIX password ...
0
votes
1answer
73 views

Payload authentication + HW-SW Binding

I want to authenticate a (2nd stage) bootloader during the boot process using a symmetric key, which is derived from HW properties of the platform the bootloader is running on. Thus, I want to bind ...
5
votes
3answers
395 views

comparing password hashing algorithms - PoC ideas?

OK so I just started working for a security consulting firm and we recommend SHA 256 (with salt) for password hashing because MD5 is too weak. I have read some brilliant answers (the list is too ...
0
votes
3answers
211 views

Security goals vs ITU-T security services

I am doing a course on cryptography, and there I learned that the major security goals are Confidentiality Integrity Availability Also I Learned that ITU-T provides 5 different security services ...
3
votes
2answers
311 views

Totally secure public key distrubition

Public-key cryptography secures communications provided that you use pre-shared public-keys. The problem is how to share these public-keys while maintaining authenticity? How can we be sure that ...
1
vote
1answer
275 views

MySQL AES Encryption - Is it good idea to store 3rd Party Auth Tokens using AES Encryption?

I need some advice on MySQL AES Encryption. I'm developing an application which connects to various 3rd-Party APIs and retrieves the Access Tokens for the application users. These Access Tokens are ...
1
vote
2answers
237 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 ...
3
votes
2answers
99 views

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
votes
2answers
561 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 ...
1
vote
0answers
233 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
votes
3answers
444 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
2k 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 ...
1
vote
2answers
2k 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
601 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
231 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
1k 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 ...
0
votes
1answer
130 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
vote
1answer
328 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 ...
6
votes
1answer
264 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
1k 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
1k 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
531 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
3k 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
233 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
265 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 ...
67
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
836 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 ...
10
votes
2answers
408 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
887 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
216 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
1k 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 ...
2
votes
2answers
563 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
151 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
649 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
689 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
615 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
750 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
491 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
474 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
512 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
6k 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 = ...