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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18
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4answers
21k views

how digital signature verification process works

I am not able to understand that how the digital signature is verified. I know that digital signature will be attached to the message and sent by sender to receiver. then receiver uses the public key ...
5
votes
2answers
1k views

Is a JavaScript implementation of AES any less secure than other language implementations?

There are a few JavaScript AES implementations available such as Gibberish-aes So assuming the AES algorithm has been implemented correctly in this library then it should be as secure as any other ...
29
votes
4answers
22k views

How does PGP differ from S/MIME?

Is S/MIME an abstracted system for general MIME type encryption, whereas PGP is more for email? Why would I want to choose one over the other, or can I use both at the same time?
8
votes
4answers
381 views

Atypical DRM situation: distribute pictures to select partners, then prevent them from reusing them

We want to distribute digital content (think pictures) to a select number of partners (around 1000, worldwide) to use as visual reference. We would like however to prevent them from copying or in any ...
1
vote
2answers
2k views

Decrypt AES 128 CTR without IV (Counter)

As the Title said: I have the cipher, the key and the counter increment function but I miss the IV (initial counter). Is there anyway for me to decrypt the message? EDIT: do we need some plaintext? ...
3
votes
3answers
687 views

Why have export controls for cryptography?

I've always heard someone justify the means for export restrictions with "it's for governmental control/spying". In most reasonable countries, the justice system asks people to adhere to the "spirit ...
14
votes
2answers
3k views

What should I know before configuring Perfect Forward Secrecy?

PFS has gained attention in our audit department because of its innate ability to limit our exposure if someone steals our private key. What pitfalls or common mistakes should I be aware of before ...
5
votes
1answer
862 views

Clarification needed for NIST's whitepaper “Recommendation for Password-Based Key Derivation”

What are some sample use-cases the NIST is supporting in this policy / whitepaper regarding PBKDF2? This Recommendation specifies a family of password-based key derivation functions (PBKDFs) ...
3
votes
2answers
635 views

Inspecting a TLS Certificate to determine RSA Key Usage restrictions

With regard to this answer, I have a question about Key Usage in an SSL certificate. Most SSL server certificates have a RSA key which is not restricted through a Key Usage extension, so you can ...
25
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5answers
22k views

What ciphers should I use in my web server after I configure my SSL certificate?

There are many great questions that ask what is the best certificate to use for a website; but once the certificate is purchased, there is also the possibility to choose or edit the Cipher list. ...
4
votes
2answers
833 views

Which is the easiest secure file transport protocol to implement (SFTP, FTPS, HTTPS, FTP over SSH, FTP over IPsec)

I have to select a secure file transfer protocol, to be implemented in a pre-boot system. I have access to libraries with the basic network functionalities (IP, TCP, UDP, etc...). I might also have ...
1
vote
5answers
10k views

How to properly encrypt a communication channel between a client and a server (without SSL)?

I have a poor knowledge in the world of cryptography, I'm just starting to learn it so I'm a newbie :) As a project for getting into the field of cryptography I want to write a client\server program ...
2
votes
2answers
1k 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 ...
5
votes
3answers
161 views

Guarding against rogue certificates

There has been a lot of news recently about certificates being falsely issued (due to the issuing authority having poor system security!). Apparently the targeted users were mostly Iranians, but it's ...
4
votes
1answer
304 views

Random number for HTTPS Message Authentication Code (MAC)

Recently I found that Netscape used quite simple algorithm to generate random number for Message Authentication Code to establish an HTTPS connection (Netscape used time, process identification ...
2
votes
0answers
278 views

Server side data de-duplication + client-side encryption with private key. Possible with “convergent encryption”? [duplicate]

Possible Duplicate: Online backup : how could encryption and de-duplication be compatible? I just saw an article on Techcrunch wherein a startup company was describing their new cloud ...
7
votes
3answers
816 views

It is possible that brute force attempts are successful before the worst case, correct?

When I read about a password being secure and stating that it would take X amount of week, years, etc. isn't that referring to the worst case? What happens if the brute force method is successul in ...
31
votes
6answers
32k views

Asymmetric vs Symmetric Encryption

I am currently taking a principles of information security class. While talking about different encryption methods a large number of my classmates seem to believe that Asymmetric Encryption is better ...
10
votes
3answers
1k views

Cryptographic Security of Dynamically Generated, Non-Random Salts

So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
10
votes
2answers
349 views

How much security is compromised if we accept other characters as login (other than the original password)?

I've just realised that facebook accepts 3 forms of a password: Source: Facebook actually accepts three forms of your password: Your original password. Your original password with the ...
47
votes
8answers
5k views

Online backup : how could encryption and de-duplication be compatible?

A "soon to enter beta" online backup service, Bitcasa, claims to have both de-duplication (you don't backup something already in the cloud) and client side encryption. ...
3
votes
1answer
1k views

Securing sensitive data in a DB,is using H2 worth it?

I am designing a web application at the moment, and one of the requirements is to secure the user credentials as well as their roles. Now of course, besides the usual password hashing + salt +.... I ...
12
votes
4answers
20k views

Recommendations for a Certificate Management tool for Linux [closed]

A client is looking to roll out OpenVPN to all its mobile employees and will use certificates on both the server and all clients. This creates a new challenge to manage all these certificates and ...
5
votes
3answers
1k views

US export control on open source libraries

I want to ask, is the US export control applicable only to US citizens? E.g. I think Bouncy Castle are Australians. Do use of their library fall into export control regulations? I do not understand ...
6
votes
3answers
409 views

Why are CA's signing keys available on the internet

I am not very knowledgeable about CA certificates, but I thought these things mainly said "The public key for bank X is Y, and this is verified by CA Z". Once you've bought this certificate, there is ...
11
votes
4answers
2k views

Multiple CAs signing a single Cert/CSR?

Just saw this suggested on Slashdot So I've seen quite a few people wanting a switch to self-signed certs (who IMO mostly don't understand what making that secure actually involves), and an idea ...
8
votes
4answers
2k views

Is using HMAC to transmit a password OK?

I'm writing a small webapp and I don't want to transmit login passwords as cleartext. As I don't have SSL available I've written a one-time challenge system which sends a random string with the login ...
23
votes
3answers
2k views

How does Convergence (CA replacement) prevent its notaries from being MITM'd as well?

I have been looking into Convergence and how it works, but I cant figure out how it is effective against a MITM attack that happens near the target system. My understanding is that Convergence works ...
16
votes
2answers
2k views

Flaw in encryption through pseudorandom number stream (from PGP documentation)

I was reading PGP docs and came upon a part written by Phil Zimmermann (PGP's creator) that piqued my curiosity: When I was in college in the early 70s, I devised what I believed was a brilliant ...
22
votes
4answers
4k views

How would you store a 4 digit pin code securely in the database?

I'm familiar with password hashing, using salts, bcrypt etc. But it doesn't seem like this would work to store a 4 digit pin code since the attacker could try all 10,000 combinations quite quickly. ...
8
votes
3answers
789 views

Does the SSL encryption strength or validation level of a website really matter?

When looking to get an SSL certificate one is presented with a lot of options. For example lets take Network Solutions since they have a nice comparison chart. Immediately there seems to be 4 major ...
3
votes
1answer
763 views

What kind of certificate do I need to be able to make and sign my own digital signing certicates?

At build time for a program, I would like to generate a new key pair, and create a certificate that will be embedded (securely) into the program. The purpose of the key pair is to digitally sign an ...
2
votes
2answers
696 views

Shortening Diffie Hellman key size through pbkdf?

I have following requirement for software I'm working on: Use strong asymmetric key exchange with public key size <16 bytes. I know it is pretty hard for this amount of bytes, but I've came up ...
6
votes
3answers
418 views

Embedded System Communications Security

I am getting ready to start deploying an embedded sensor network that is internet connected (via the cell network) and reports private data on a regular basis back to a central server. Unfortunately, ...
38
votes
2answers
4k views

Pre-hash password before applying bcrypt to avoid restricting password length

Good practice is not to unnecessarily restrict password length, so that appropriately-long passphrases (perhaps 35-45 chars for 6/7 dicewords) can be used. (See e.g. Should I have a maximum password ...
12
votes
5answers
6k views

How can I decrypt data with Java, without hard-coding the key?

I hope this is not a chicken-egg problem or reinventing the wheel but here goes. I have a Java application that needs to access a password protected file (actually during the application startup). The ...
9
votes
3answers
1k views

Is TDEA (TripleDES) invulnerable to the weak keys of DES?

The key space of DES includes some keys that are weak, which results in a ciphertext that is extra vulnerable to cryptanalysis. Is TDEA (also known as TripleDES) invulnerable to those weak keys? Or, ...
4
votes
4answers
1k views

AES ECB Mode for single block/random data encryption

I need to save random 16 byte keys to a database. To encrypt these keys I currently use AES 128 with ECB Mode (because of smaller data to store, no IV needed), but now I read a lot about ECB being ...
8
votes
5answers
6k views

How would one fully protect himself against man in the middle-attacks? [closed]

Imagine I have a computer where all the trafic is being sent through the MitM. How would it be possible to have a secure connection through this setup? In this case it would be OK to design a new ...
1
vote
2answers
881 views

Which encryption algorithms will be used to replace RSA when quantum computers become common? [duplicate]

Possible Duplicate: Are the encryptions "broken" with great computing power? I just wondered which algorithms will be used once quantum computers become common. Are there already ...
238
votes
13answers
27k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
11
votes
1answer
789 views

Any risk in using the same salt for several hashes on a user?

Right now I'm storing a salt and password_hash on the users table (pretty standard stuff). The need arose to get a secure hash of another field for a user. Is there any risk in reusing the same salt ...
8
votes
7answers
2k views

Is there any asymmetrically encrypted file system?

Is there a file system providing a directory where everybody can write, but only the directory owner can read the files? In theory it could be done by encrypting using the public key while writing, ...
3
votes
2answers
1k views

Is this algorithm for a random string cryptographically secure?

I've pieced together this algorithm (if it can be called that) from various bits of code I've seen online, and I'm wondering how cryptographically secure it is. It's used to generate passwords: ...
49
votes
2answers
12k views

Amount of simple operations that is safely out of reach for all humanity?

Cryptographic primitives usually assert some security level given as number of operations to mount an attack. Hash functions, for example, give different security levels for collision attacks, ...
660
votes
21answers
133k views

XKCD #936: Short complex password, or long dictionary passphrase?

How accurate is this XKCD comic from August 10, 2011? I've always been an advocate of long rather than complex passwords, but most security people (at least the ones that I've talked to) are ...
6
votes
2answers
764 views

Do Flash memory (SSD) architecture impacts encryption techniques?

I'm working on encryption techniques on SSD's and my question is: does the erase before write architecture of SSD's has anything to do with the encryption technique? What are the problems I might ...
14
votes
4answers
10k views

Is it possible to securely store passwords using reversible encryption?

Everyone says that you need to use a non-reversible hash when you store passwords so that even if your database is leaked, the passwords themselves are still safe. I'm wondering if there is anyway to ...
21
votes
2answers
4k views

Is “real salt” the same as “initialization vectors”?

In the question about real vs. fake salt, the answers describe how real salt 'perturbs the encryption algorithm.' I know roughly how initialization vectors work; is this the same concept, or something ...
40
votes
7answers
3k views

“Real” Salt and “Fake” Salt

During a Q&A period at DEFCON this year, one member of the audience mentioned that we're using "fake salt" when concatenating a random value and a password before hashing. He defined "real salt" ...