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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13
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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?
1
vote
1answer
183 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
865 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
votes
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
620 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
votes
3answers
788 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 ...
28
votes
5answers
48k 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
620 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
350 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
186 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
745 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
311 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
22k 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
375 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
529 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
905 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
978 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
198 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
109 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
266 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 ...
-1
votes
1answer
173 views

How Does VMWare Protect Passwords? [closed]

I am interested what features VMWare uses to protect passwords inside the virtual machine.
2
votes
2answers
600 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
211 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
650 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 ...
2
votes
1answer
547 views

X.509 certificate policy mapping question

So I'm a little confused how X.509 certificate policy mappings work. So let's say the following depicts my cert chain: root CA ---> intermediary CA ---> client cert Would the root CA have a ...
6
votes
2answers
3k views

Explain the naming with the variety of cipher-methods as seen by `$ openssl enc --help`

I am confused by this variety, perhaps outlined here. I am trying to understand the conventions. Trend A: strength? $2^8$, $2^7$ -- seems clear but why algo with 192 or 40? Referring to same issue? ...
4
votes
1answer
613 views

Does KASUMI (A5/3) Related Key attack apply to 3G or other mobile providers?

The KASUMI is a block cipher used to encrypt UMTS, GPRS, and GSM SMS messages. The references section in Wikipedia says that a related key attack is possible in 3G systems. Q: Has it been proven ...
7
votes
3answers
2k views

Why does OpenVPN require securely sharing certs with clients?

The ubuntu docs on OpenVPN have this part in the instructions: Copy the following files to the client: /etc/openvpn/ca.crt /etc/openvpn/easy-rsa/keys/hostname.crt ...
4
votes
2answers
1k views

How long shall a certificate be valid?

See title. Are there any sources where there are recommended validity times of certificates (based on length, algo, etc)? I'm particularly interested in validity of RSA certificates...
2
votes
3answers
659 views

What is the recomended algorithm to create a key from a password?

In my new secret document encryption utility, the key for symmetric encryption = the hash of a random salt and a user provided password. It is necessary to have a slow hash function in order to ...
3
votes
3answers
442 views

Public key system confusion

I read the following about PKI: Using a public key system, a user may encrypt a portion of a document using his or her private key. This message will later be decrypted by the recipient using ...
4
votes
2answers
582 views

Could the bcrypt-ruby binding be vulnerable?

While developing a Ruby on Rails application using a commonly used authentication library named devise, I noticed from the prefix $2a$ of the produced password hashes in the application database that ...
10
votes
6answers
2k views

Prevent denial of service attacks against slow hashing functions?

I've been thinking about bcrypt recently, and what I wonder is if there's a way to deal with the inherent (D)DoS problems with slow hashing functions. Namely, if I set up bcrypt so my machine takes ...
0
votes
1answer
43 views

Secure intermediation of messages

Suppose there's systems A, B and C. A has an trusted relationship* with B and B has one with C. How can B intermediate a request from A to C while still providing both A and C the guarantee that ...
2
votes
1answer
2k views

Explanation of SSL handshake with certificate

I've read a lot of articles. The client uses the information sent by the server to authenticate the server. If the server cannot be authenticated, the user is warned of the problem that an ...
4
votes
2answers
5k views

Confusing about Ephemeral Diffie-Hellman

1 Does Ephemeral Diffie-Hellman support authentication? Quote from www.rsa.com/products/bsafe/documentation/mesuite21html/dev_guide/group_EPH_DH.html Ephemeral Diffie-Hellman does NOT provide ...