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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For what malicious activity can one use a computer with a high-end GPU?

I'm currently researching what malicious activities can one do with a computer containing a high-end GPU. So far the only uses I found were Bitcoin mining and password cracking. Are there any other ...
1
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1answer
517 views

Best Practices for Storing Digital Certificate

I'm building an application where certain sensitive files need to be digitally signed before being stored in the file system using ASN.1 encoding, so they can be verified against a digital certificate ...
10
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3answers
1k views

HMAC Based Request Signing - Storing the Salt

I'm working on a (non high security) project that currently isn't live but might go live at some point. We have a REST API (implemented using Restlet and Neo4j) running on a server and an Android ...
2
votes
2answers
942 views

Is it true that encryption bit “strength”, although numerically identical, may actually be different depending on the algorithm?

I was reading recently that for AES, the encryption strength is actually the key size/length, so 128-, 192- or 256-bit. While, for SHA-2, the encryption strength is measured against the message digest ...
4
votes
3answers
252 views

What would the cryptographic impact be of knowing the output of /dev/urandom?

Another noob question, I know, but something I'm unsure about. If I somehow magically knew the output of /dev/urandom at any given time, how much would that weaken a given encryption system? Or, ...
1
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1answer
739 views

Is using the same RSA key pair for both (signing and encryption) & (signing and encryption) a bad idea? [duplicate]

Possible Duplicate: Why should one not use the same asymmetric key for encryption as they do for signing? I'm new to IT Security. I still can't figure out why using the same RSA key pair ...
4
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2answers
1k views

MAC vs Encryption

I understand the difference between MAC (eg. hmac_sha256, etc.) and Symmetrical Encryption (eg. rc4, etc.), but my question is what advantage does MAC solve that using encryption doesn't? I know that ...
4
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1answer
3k views

Is BCrypt enough when saving a password into a database?

In order to allow users to connect to my website, I encrypt their password using BCrypt since it is one of the slowest algorithms to decrypt (making a compromised database longer to be decrypted). ...
26
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3answers
20k views

What is ECDHE-RSA?

What is the difference between ECDHE-RSA and DHE-RSA? I know that DHE-RSA is (in one sentence) Diffie Hellman signed using RSA keys. Where DH is used for forward secrecy and RSA guards against MITM, ...
3
votes
4answers
869 views

Can we prevent a man-in-the-middle attack with symmetric-key cryptography?

Suppose that Alice signs the message M = "I love security" and then encrypts it with Bob's public key before sending it to Bob. As well known, Bob can decrypt this to obtain the signed message and ...
1
vote
1answer
792 views

SRP 6a implementation C#

I'm trying to implement the SRP crypto; 6a. However I'm not familiar with the cryptography and it's computing. I'm using the public implementation of the BouncyCastle lib, but I have no idea how it ...
15
votes
3answers
613 views

If I have two identical linux virtual machine images, will they generate identical random numbers?

A really noob question, I know, but something I was wondering about this morning. If this were the case, would they encrypt things identically? Or maybe someone could direct me to a helpful research ...
14
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1answer
10k views

What is the actual value of a certificate fingerprint?

In a x509 digital certificate there is a "certificate fingerprint" section. It contains md5, sha1 and sha256. How are these obtained, and during the SSL connection, how are these values checked for?
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vote
1answer
184 views

Stripping / appending characters from user password before hashing to conceal it forever?

I had this idea to permanently conceal user password by requiring minimum length then stripping certain characters. For example if the user password is secret123, the system will strip it down to ...
4
votes
3answers
881 views

Pseudo Random Generator is not initialized from the (entropy pool)?

The RHEL5 manuals state that /dev/urandom will use the entropy pool until it's exhausted, and then it will resort to a fall-back pseudo-random algorithm, so that it will never block. But when ...
4
votes
2answers
3k views

Is your PGP passphrase used to decrypt an encrypted private key, or needed in conjunction with the private key to decrypt the message?

If the former, then if the private key can be used to digitally sign messages, why doesn't your client offer to encrypt this highly sensitive piece of data? If the latter, then if someone had access ...
8
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3answers
1k views

Hashcash, is this really used?

I just heard about this term, is it really used? The concept does not seem new, is it used and/or implemented in current technologies?
3
votes
2answers
625 views

Can key files be brute-forced like passwords?

Let's say you use a program like Truecrypt or Keepass which allows you to have a password + key file. I understand that passwords can be brute-forced/dictionary-attacked but is the same true for key ...
6
votes
4answers
1k views

Does a CA need to have the same type of key as the certificates it is signing? RSA / Elliptic Curve (EC/ECDH/ECDSA)

I am making a CA that I hope to be able to sign RSA and Elliptic Curve-capable (EC) keys with. I was wondering if the best approach was: CA with RSA keys capable of signing RSA and EC CSRs CA with ...
5
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3answers
830 views

TLS Renegotiation Indication Extension vulnerability

I am trying to understand the TLS Renegotiation Indication Extension from the RFC. I can understand that it is related to the fact that the renegotiation is sent under the encrypted stream, but I ...
29
votes
5answers
51k views

Why most people use 256 bit encryption instead of 128 bit?

Isn't 128 bit security enough for most practical applications?
3
votes
1answer
2k views

how do extended validation X.509 certs work?

https://www.forumatic.com/ uses an extended validation cert. wikipedia.org's entry on extended validation certs says that a cert is known to be an extended validation cert if the OID in the ...
2
votes
3answers
10k views

What does these warnings mean on an SSL connection by firefox (only)

I am connecting to a secure site and firefox mentions about identity: Owner: This website does not supply ownership information Verified by: Not specified Technical Details: Connection ...
2
votes
1answer
668 views

Is SSL session based only? Is there a (formal) definition of an SSL connection?

In various docs on SSL there is a mention of connection. But from the context I am not sure if this means the underlying TCP connection or the SSL connection. I am thinking that there is no SSL ...
1
vote
1answer
353 views

What are the requirements for a random number generator to a be safe to use in cryptography?

When I look at most RNG's (random number generators), I see a disclaimer that looks similar to this: Caution: Mersenne Twister is basically for Monte-Carlo simulations - it is not ...
2
votes
1answer
3k views

Convert RSA public key to the right format

I need to send a public key to my bank. I'm using CoreFTP which allows the generation of keys using RSA. It says that it generates "OpenSSH compatible certificates [sic]" when you press the generate ...
2
votes
1answer
189 views

Browsers and export regs. Is SGC still valid?

I was reading a rather "dated" book on SSL/TLS, which mentions about International Step Up certificates and Microsoft's Server Gated Certificates which were the way arround the US export rules for ...
0
votes
1answer
762 views

Should I use Windows' Cryptographic Service Provider to generate RSA keys?

If I want to generate strong high quality RSA keys, is there any reason not to use Microsoft's built-in cryptography system? Or should I use something open source like OpenSSL or Bouncy Castle? I'm ...
0
votes
2answers
2k views

How to prevent file duplication/burning of a CD/DVD

I have HTML and SWF files that I want to put on a CD. How can I protect the contents on the CD, or make it difficult for someone to burn or duplicate them?
3
votes
4answers
312 views

Is there a crypto system which detects decryption somewhere between sender and receiver?

I was wondering if there exists (or if it could be created) a cryptographic system in which a message is encrypted and sent from A to B, and some nodes in the middle could intercept and decrypt the ...
3
votes
1answer
315 views

Encryption on the GPU, safer or not?

I was just wondering whether performing encryption on the GPU was safer than on the CPU, with regard to the difficulty of reading the encryption key from memory and/or various other hardware attacks. ...
3
votes
4answers
23k views

how safe is the 256 bit encryption used in bank transactions

Most of the banks use a 128 bit or 256 bit encryption. What does this mean? Does it mean that the keys used in ssl are 128 bit long or what? If they are the ssl key lengths then 128 bit rsa keys are ...
6
votes
4answers
3k views

HMAC/PBKDF2 vs Simple hashing algorithm for web service authentication?

We are in the process of creating a web service and have been investigating ways of securing it. In reality, the service is likely to get very little traffic and the data is likely to be of little use ...
9
votes
3answers
8k views

What is the DUKPT Key Derivation Function?

I'm tasked with decrypting ciphertext acquired from an encrypted card reader. The card reader utilizes DUKPT(derived unique key per transaction) scheme and 3DES encryption. I don't have a problem with ...
0
votes
3answers
393 views

Where can we learn more about recursive encryption schemes?

I've been wondering about recursed encryption. The idea I'm trying to convey here is an encryption scheme where a message is encypted, then somehow encrypted again, and again, etc. The encryption ...
2
votes
4answers
534 views

Demonstration of how security through obscurity fails to work

I need to demonstrate that security through obscurity fails twice in the following scenario. I've a secret KEY. User A gets MessageX = SecretTransformation(KEY, SecretValue1); User B gets MessageY ...
29
votes
4answers
6k views

How can PrivateSky not see your data?

PrivateSky is a website that promises encrypted "cloud-like" secure information exchange. They promise that except the sender and receiver, nobody can see your data. After testing it yesterday, I do ...
4
votes
1answer
909 views

How secure is TOTP key on phones?

Our company is considering several options in moving to MFA with software OATH TOTP or yubikey OATH OTP. In regards to where the secret is stored, I'm aware that a yubikey or similar hardware device ...
20
votes
5answers
4k views

What's the practical limit for rainbow-table based bruteforce?

Say we have a hash of a password. The password can be considered to be made of of totally random characters and has a fixed length of N. The hash is SHA1(password+salt), where the salt is of length M. ...
4
votes
3answers
996 views

Diffie Hellman - how large should the random number be?

When using the Diffie Hellman exchange with the second Oakley group 1024 bit Prime per RFC 2409 (*), how large should the random numbers generated by both sides be? In RFC 2631 this is called the ...
3
votes
1answer
200 views

Recover file using Java RanNum Gen + Key

EDIT: Here is some more background. I am basically trying to reproduce this the method outlined here I have been able to hit everything up until the paragraph regarding the decrypting of the data file ...
8
votes
2answers
2k views

Taxonomy of Ciphers/MACs/Kex available in SSH?

SSH offers a large variety of algorithms for Ciphers, MACs and KexAlgorithms configuration options. Sometimes I need quick and light (my own internal network), and sometimes I want all the ...
1
vote
1answer
111 views

valid intermediate certs not in browser

Say an X.509 cert is signed by an intermediate cert that's not in your browser. Maybe the root certificate is but not the intermediate cert. At that point it seems like a valid certification path ...
3
votes
3answers
271 views

Does the hash change the security of the Secure Remote Password protocol?

I'm implementing the Secure Remote Password protocol, and similar to this question, I'm wondering if I can use the SHA-512 hash function instead of SHA-1 currently being used. Would this help improve ...
7
votes
1answer
2k views

How will security need to be changed if P=NP?

If we suppose that it is found that P=NP, how will security measures need to be changed? I'd like to know the major security measures that are affected, and how they would need to be changed. We can ...
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votes
1answer
174 views

How Does VMWare Protect Passwords? [closed]

I am interested what features VMWare uses to protect passwords inside the virtual machine.
2
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2answers
619 views

Why is using a pseudo-random key considered more practical than a one-time pad?

I am experiencing confusion regarding one-time pads. I have read that a one-time pad generates a key that has the same length as the plaintext. This is considered to be an overhead in sharing such a ...
2
votes
3answers
3k views

Intercept data sent via bluetooth

I am trying to re-write a closed-source application, originally deployed on mobile devices, that lets you command and control a certain type of mechanical robots via bluetooth. The new application I ...
3
votes
2answers
215 views

self-signed certs that aren't the final certificates in the path

The X.509 spec makes frequent statements like this: (b) If certificate i is self-issued and it is not the final certificate in the path, skip this step for certificate i. How can you have ...
8
votes
2answers
667 views

X.509 certificate policies question

I asked another question about certificate policy mappings. This is a different issue. This is about Certificate Policies. To quote from the X.509 RFC: In an end entity certificate, these ...