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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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
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2answers
1k 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
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4answers
3k 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
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3answers
780 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
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1answer
734 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
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2answers
686 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
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3answers
400 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
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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
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5answers
5k 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
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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
864 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 ...
235
votes
13answers
25k 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
763 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
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7answers
1k 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: ...
47
votes
2answers
11k 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, ...
640
votes
21answers
129k 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
759 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
9k 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 ...
39
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7answers
2k 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" ...
7
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2answers
4k views

How large blocks does AES-cbc use with a 128 bit key and with a 192-bit key?

I read on wikipedia that the AES with cipher block chaining and a 128-bit key uses blocks of size 128 bit to encrypt the data. However, it also said that with a 192-bit key, there were still 128-bit ...
7
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3answers
922 views

Server to server encryption: Key rotation over the air. Can it improve security?

In my other question, I explored whether to write my own encryption or use an existing one. I was advised to use TLS or AES or something that is established. This question is about key rotation. It ...
7
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2answers
2k views

Dictionary Attack on Wifi

I know a few people with pretty weak passwords. What kind of systems exist to prevent dictionary attacks? Would it make sense to restrict the number of connection attempts in a certain timeframe? ...
7
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2answers
409 views

Geographic equivilent of RFC 3161 (X.509 PKI Time-stamp Protocol)

First time poster here, hope to be around more often. I'm in need of a cryptographically secure 'stamping' system that allows not only time but also location to be attached to data, while still ...
12
votes
1answer
411 views

What did Blackberry do wrong?

The NIST defines a vulnerability in RIM Blackberry encryption discovered last October. Apparently, Blackberry's flavour of PBKDF2 was weak. They say: The offline backup mechanism in Research In ...
18
votes
3answers
3k views

Convergence - an SSL replacement?

Today, Moxie Marlinspike, a security researcher famous for his research on Android and SSL and related protocols (author of sslstrip/sslsniff), released "Convergence" which says is "an agile ...
3
votes
2answers
2k views

Truecrypt hidden partition deleted original drive data

Help! I created a hidden partition within a harddrive encrypted using truecrypt, and instead of creating a second partition, it seems to have deleted all of my data instead. what did i do wrong? I ...
4
votes
1answer
693 views

Slow client key exchange in TLS?

I've been benchmarking my TLS performance, and I noticed that during the "write client key exchange" phase, there's significant overhead compared to all other actions. I'm wondering if there's ...
7
votes
8answers
889 views

Is the following authentication scheme secure?

I was trying to design an authentication system that would make it much harder to guess a password via brute force, and reduce the risk to a user if the hashed password was stolen through a snooping ...
5
votes
3answers
398 views

DHE exchange and client authentication

If a server has a known public key and a Diffie-Helman exchange is performed and signed by that key, is there any benefit to authenticating the client before establishing a secure channel instead of ...
11
votes
1answer
1k views

Native rsync protocol security

Is the native rsync protocol (port 873) secure? Does it encrypt data or credentials? I'm planning on using rsync to store encrypted files in the cloud, I'm wondering whatever the password is ...
5
votes
2answers
337 views

Is cascading cryptographic algorithm better than using a single one?

Am I wrong to think that scrypt(bcrypt(password)) would be better than using sole (s|b)crypt? Especially when considering two different key for the two algorithms. I am also interested in some ...
2
votes
2answers
2k views

DUKPT - Sample data other then in X9.24

I wrote some code that does PIN encryption/decryption according to rules in X9.24. It works great with examples provided in ANSI doc, but doesn't work with actual device from the client. Where can I ...
3
votes
3answers
1k views

AES for key encryption

Is AES a good choice for protecting a key stored on the computer of a user of my application? I have seen threads on hashing passwords that suggest using slow algorithms for defending against brute ...
28
votes
7answers
15k 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 ...
4
votes
1answer
298 views

self-signatures using SHA1

This page says: self-signatures must not use SHA1 You can check this by doing: gpg --export-options export-minimal --export <keyid> | gpg --list-packets |grep -A 2 signature|grep ...
6
votes
2answers
494 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 ...
35
votes
15answers
5k views

Why do people think that this is bad way to hash passwords?

Well, please tell me, what's wrong with this code: $password = "hello"; $password = md5($password); for($i=1;$i<20;$i++){ $password = md5($password); } It's exactly the same as this one: ...
0
votes
2answers
807 views

Best ways to store a password Server side [closed]

I was using Lotus Notes today and I realized that the program asks password is encrypted in many ways. even without access to the stored passwords notes I can say that they are at least as recorded in ...
7
votes
2answers
2k views

SSL Session resumption and IDs

Some sites, as seen in the report for www.mbank.com.pl [ssllabs.com] or report for aliorbank.pl [ssllabs.com] do not support "Session resumption", either because IDs are assigned but not accepted ...
14
votes
2answers
2k views

What are the most common password salting methods?

I learned that the Sun guys used the login name as salt for password hashing. Is this a common approach? What are the most common salt values?
9
votes
2answers
5k views

Is 1024bit Diffie Hellman key exchange secure?

My system uses AES-256, 4096bit RSA CA key and 2048bit RSA keys for servers together with SHA-256 signing. Does using 1024bit DH key exchange lower its security? I read on one mailing list that ...
11
votes
2answers
2k views

Which cipher suites with AES cipher provide forward secrecy?

Does standard AES with RSA (reported by Opera as TLS v1.0 256 bit AES (1024 bit RSA/SHA)) provide perfect forward secrecy? Which SSL3.0 and TLS1.0 ciphers do provide forward secrecy? Which ciphers ...
6
votes
3answers
12k views

Which type of encryption algorithms android supports, and which would be better?

I read this documentation, and I have written an algo to encrypt and decrypt a string. But I don't know how many types of algorithms android supports. Regarding DES and AES (As wiki documentation) ...
6
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6answers
2k views

Are there any “real world” implementations of secret-sharing encryption schemes?

Imagine something like TrueCrypt where user A can decrypt his files, or any 3 of the 10 directors in his organization can decrypt user A's files. As I understand it this is similar to the way the ...
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vote
2answers
9k views

What are private key cryptography and public key cryptography, and where are they useful?

I don't understand the real world usage scenarios of these cryptography methods. Can any one please explain how they work, with examples and also their usage in the real world?
12
votes
4answers
565 views

Encrypting data by parts vs encrypting the whole data

Suppose I have a file with records, and I have two options to encrypt it: encrypt the file as a whole encrypt each record separately and store them together. Which way is generally preferable and ...