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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3answers
938 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
196 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
108 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
258 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
169 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
585 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
204 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
609 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
522 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
2k 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
587 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
953 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
647 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
429 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
567 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
42 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 ...
21
votes
2answers
6k views

What is the difference between a Hash Function and a Cryptographic Hash Function?

I mean, is it just a matter of "how difficult is it to reverse the function with the current technology"? Or is there a mathematical concept or property that makes them different? If it is a matter ...
3
votes
5answers
1k views

TrueCrypt dataleaks that might betray the “Deniable File System” option

Reading into "Operation Satyagraha", one would have to believe give all the resources used that the investigators had some reason to believe there was data to decrypt, even though in theory and in ...
0
votes
1answer
286 views

id-ce-cRLDistributionPoints ASN.1 / DER encoding question

I have a file - test.pem - with the following contents: -----BEGIN CERTIFICATE----- MBIwEKAOoAwwCqMIMAZhBEFCQ0Q= -----END CERTIFICATE----- openssl asn1parse -inform PEM -in test.pem -i returns the ...
2
votes
2answers
199 views

OpenPGP: Sign-Verify workflow without Encrypt-Decrypt?

Is it a good and/or frequent practice to sign a file (with your own private key) without encrypting it (with the intended recipient's public key?) I haven't really been able to find a direct answer to ...
2
votes
1answer
519 views

question about implicitly tags in ASN.1

From the X.509 RFC, in the "Implicitly Tagged Module" section: CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint DistributionPoint ::= SEQUENCE { distributionPoint [0] ...
0
votes
1answer
500 views

How does FileVault 2 work with multiple decryption keys?

With FileVault 2, you can encrypt the hard-drive such that users on the computer can decrypt it with either of their passwords How does this work?
3
votes
1answer
2k views

Storage of 'secrets', keystores, HSMs and the rest

I've been digging for the past few days into storage of sentitive data. If I store this data in a database, I believe the general accepted practice is to store sensitive data encrypted, for various ...
0
votes
5answers
857 views

What voip client support manual encryption?

In pidgin there is a plugin that we can use to encrypt our messages in chat windows .. Is there anything simular for voip (pc to pc) ? any client that support manual encryption for voice data?(linux)
4
votes
2answers
4k views

Recommended Cipher Suites for TLS 1.0, 1.1 and 1.2

There are a lot of cipher suites defined in the in the specifications itself of TLS 1.0, 1.1 and 1.2. And furthermore, there exist RFCs which add even more cipher suites to a specific version (e.g. ...
0
votes
1answer
751 views

Is Data Object on openPGP smartcard v2 encrypted?

currently I thinking about on-the-fly disk encryption using Truecrypt/dmcrypt LUKS with key stored on smartcard. I would like to use openPGP v2 smart card, respectively GPF Cryptostick which is based ...
13
votes
2answers
3k views

How big salt should be?

I will be using scrypt to store passwords in my application. As such, I'll be using SHA-256 and Salsa20 crypto primitives (with PBKDF2). Having that in mind, how big salt should I use? Should it be ...
2
votes
3answers
178 views

Closed Port security

I have what I think is a security IT question (I'm more of a programmer myself). Assuming I am running a dedicated machine (say a PC) for a single program, meaning that the only port visible and open ...
2
votes
2answers
286 views

Does secure remote password verifier transmission need to happen out of band?

With relation to the necessity of a verifier being transmitted from the client to the server prior to any handshake steps, I was wondering how this is supposed to happen securely? To me this seems ...
4
votes
1answer
849 views

Bcrypt as a key derivation function?

I read a lot of entries at stack exchange about bcrypt and why it is supposed to be better than PBKDF2 in terms of password storage. I'm asking now if bcrypt is better than PBKDF2 in terms of key ...
5
votes
2answers
629 views

Zero padding in HMAC

Section 2 of RFC 2104 defines the key used in HMAC should be padded with zero bytes up to the block length of the underlying hash algorithm. Isn't this a potential security vulnerability since any key ...
3
votes
4answers
492 views

Base64 conversion for byte array in encryption

I am using ECC algorithm for security. Now the concern is I am placing the data in web page after encryption of the data in hex format and transmit to server and then it decrypts the data, but when I ...
4
votes
2answers
2k views

openssl_digest vs hash vs hash_hmac? Difference between SALT & HMAC?

openssl_digest vs hash vs hash_hmac I want to use SHA512 for storing password. Which of the above methods are best to use? Why? What is the difference between SALT & HMAC? I just read ...
3
votes
2answers
3k views

HMAC key value and security

What effect would there be if you used the same value you were hashing as the Key in an HMAC? For instance given the following example: message: "my secret message" nonce: ...
4
votes
1answer
844 views

X.509 algorithm identifier parameters vs. extension values

From the X.509 specs: AlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL } ...
3
votes
1answer
1k views

Why doesn't asn1parse parse all DER encoding strings?

I have a file - crl.txt - that contains the following: MDYwNKAyoDCGLmh0dHA6Ly93d3cyLnB1YmxpYy10cnVzdC5jb20vY3JsL2N0L2N0cm9vdC5jcmw= It's from one of the extensions in a particular X.509 cert. Why ...
15
votes
3answers
2k views

What is a cryptographic oracle?

I came across the term "cryptographic oracle" and despite a bit of googling I was unable to come across a clear, concise definition. What is a cryptographic oracle and what does it do? Can anyone ...
4
votes
1answer
338 views

Thoughts on creating unscalable conditions to brute force even small passwords?

I stumbled upon something called "scrypt" which claims to add fixed time/space complexity requirements into password-based key derivation. Quoting from their page: A simple password-based encryption ...
3
votes
1answer
1k views

parsing the id-ce-keyUsage extension in X.509 certs

I'm trying to decode an X.509 certificate and have a question regarding the decoding of the extensions. In particular, the octet string corresponding to id-ce-keyUsage (OID 2.5.29.15) is as follows: ...
4
votes
2answers
95 views

Methods of accessing CRLs

I'm creating custom certificates with CDP Definitions with the option of configuring several methods of accessing the CRL. My options are HTTP, LDAP, and FTP. What are best practices or should I say ...
21
votes
6answers
7k views

Is AES encrypting a password with itself more secure than SHA1?

This isn't really a practical question, but more a question of curiosity. I heard a CS professor recommend stepping up from md5ing passwords not to SHA1, but to AES encrypting the password using ...
3
votes
1answer
162 views

Does knowing encrypted information make it easier to find an unknown key?

I'm curious if knowing the exact content of an encrypted message or several messages makes it theoretically any easier to discover the encryption key. Does this speed up a brute force attack in any ...
3
votes
1answer
1k views

static IV and random keys using aes-256-cbc

Are there any security risks in using a static IV if I generate a new random KEY for each set of data to encrypt? If I understand correctly what the purpose of the IV is in Cipher-block chaining mode ...