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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14
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8answers
3k views

Is advanced mathematics relevant to security beyond cryptography?

Short question. The title says it all... is advanced mathematics (i.e. beyond the classic college level calculus sequence) relevant to any field of computer security besides cryptography? By relevant, ...
17
votes
3answers
6k views

What specific padding weakness does OAEP address in RSA?

It's been recommended to use OAEP when padding messages to be encrypted via RSA, to prevent known plain text attacks. Can someone elaborate this in better detail? I'd specifically like to know the ...
4
votes
3answers
424 views

Can encryption twice with two keys in different sequences lead to the same result?

I am looking for an encryption algorithm for one of my current papers. The basic requirement is that, suppose I have two keys k1 and k2, and the E(k1,t) means encrypt t with key k1. Are there any ...
2
votes
2answers
574 views

How high is the entropy of this salt-generating code? (No code-reading actually necessary)

What is the best method? Assumption: I have a function that generates a number of medium-high entropy bytes Step1: I generate 3 of these medium-high entropy bytes. Step2: I hash these bytes using a ...
4
votes
1answer
250 views

Potential issues with Kim Dotcom's new proposed “encrypted webmail service”

Just spotted a Reddit thread about Kim Dotcom, of MegaUpload fame, planning to produce a secure webmail system that allows people to communicate securely, without the worry of having their messages ...
5
votes
5answers
36k views

Cracking CISCO ASA Passwords

I've got a copy of a Cisco ASA config and i want to crack the following example passwords I've got the following lines in the config ASA Version 8.4(2) ! hostname ciscoasa enable ...
4
votes
2answers
221 views

Ethernet security

I have a simple question that many people probably have and yet there does not seem to be a topic on this. I am visiting a company for a meeting and I have my laptop with me. This company is our ...
4
votes
2answers
7k views

How X509 Certificates are used for Encryption

I have small doubt regarding the process of X509. I am aware of OpenPGP Encryption/Decryption, where we generate the public key and private key. We can share the public key to vendors and they can ...
3
votes
5answers
1k views

The security level in hash function

What is the difference in security between using part of message digest hash function or all the message digest hash function? and is there any equation can calculate the security for part or whole ...
5
votes
2answers
1k views

Is it reasonable to prevent timing attacks by using fixed processing time

I have systems that perform cryptographic operations within a SSL/TLS tunnel. My concern is that I may leak timing information when encrypting, decrypting, or hashing. Part 1 Is it a good idea to ...
3
votes
2answers
320 views

Securing Time Sensitive Data

I have a number of time sensitive, embargoed pieces of information that I need to distribute over the Internet and have received at a precise time. I'm currently dealing with the problem by uploading ...
2
votes
1answer
1k views

sha-512 vs sha-3? [duplicate]

Does the new SHA-3 Keccak hashing algorithm offer any benefits from SHA-512? "Even worse, none of the SHA-3 candidates is significantly better. When SHA-3 is announced, I'm going to recommend that, ...
1
vote
2answers
6k views

Why does OpenSSL not include AES-256-GCM? [closed]

I'm trying to implement AES-256-GCM in Ruby. Ruby's OpenSSL wrapper library and aead library both clearly seem to believe that OpenSSL itself supports this. However, neither 0.9.8r (which I had ...
0
votes
4answers
822 views

Is using the md5 hashing algorithm as method for authorization in an HTTP POST request unsafe?

I am creating a page on a website that will show a user some authorized information from another website, and that website uses a combination of the user's user-number and a secret passphrase hashed ...
0
votes
1answer
133 views

Securing the SOAP Messages

One of my clients wants to encrypt few sensitive information which will be transferred through webservices / SOAP. My client has the following suggestions: Encrypt the sensitive data with AES ...
3
votes
1answer
2k views

aes cfb 128 decryption /encryption problem between Erlang and PHP

Update 2 - it works Thanks to Tom Leek for his answer. The CFB mode of mycrypt for Rijndael uses a 8-bit feedback loop and not a feedback loop the length of the key/iv. You have to force it to use ...
5
votes
3answers
519 views

Use of rainbow tables with the NY Times hack?

The NY Times recently published a story about how they were hacked during a four month period. The hacks allegedly were carried out by part of the Chinese military. One part of the story that ...
2
votes
2answers
179 views

Easy protocol for email authentication

I'm cooking up a very simple system to send commands to a remote server via email. Everytime an email is sent to do_something@mydomain.net, the server runs a python script that does something ...
3
votes
4answers
743 views

Can an attacker reuse stolen SSL private key to recreate that domain on his server

Say my domain (https://example.com) SSL private key has been stolen and was not protected by a passphrase then. Can the attacker uses that key and certificate to host the same domain on different ...
4
votes
2answers
2k views

What are the differences between ssh generated keys(ssh-keygen) and OpenSSL keys (PEM)and what is more secure for ssh remote login?

I have learned there are 2 methods to make SSH remote login easier and secure , those are; ssh generated keys (using ssh-keygen)OpenSSH Keys PEM (.pem) keys usually generated with OpenSSL (Amazon ...
0
votes
2answers
474 views

What is the best way to generate keys in phpseclib?

I am using phpseclib implementation AES and HMAC. But I dont know the best way to create random keys for these. What is the best way to do? Is there any built in function in phpseclib to create keys ...
0
votes
2answers
2k views

What is the difference between protocols and algorithms? [closed]

I am learning network security and I can't understand the boundary line between protocols and algorithms. Are algorithms the concrete realization of the protocols? Are protocols composed of several ...
1
vote
6answers
2k views

Is SHA-1 encryption?

I have read that SHA-1 is a cryptographic hash function. On an exam, SHA-1 was given as a possible one-way encryption algorithm. Does SHA-1 require a key as input? Is a key required to qualify as ...
2
votes
4answers
2k views

SSH: reusing public keys and known-man-in-the-middle

Usually, people recommend to use a single private-public key pair everywhere (if we're not talking about a possibility of compromising the private key): Best Practice: “One per-user ssh key” or ...
0
votes
3answers
187 views

Maintain sensitive key between requests

EDIT: Reworked question. Previous version too poorly asked. On my website users write sensitive messages that must be kept secret. The entire user area is over SSL, so the communication between user ...
0
votes
1answer
206 views

Tracking information on HTTPS connection

My organization uses cyberoam firewall. They are monitoring all activities including my search text in Google, Wikipedia etc. So recently i changed to HTTPS versions and now using HTTPS connections of ...
0
votes
1answer
777 views

Is TLS secure when full eavesdropping on the network occurs? [duplicate]

Possible Duplicate: How is it possible that people observing an HTTPS connection being established wouldn’t know how to decrypt it? Alice connects to Bob's site via a TLS secured connection ...
3
votes
3answers
1k views

Hash Function Xor

For a hash function what is the best secure method, XOR or Concatenate: h(data1 XOR data2 XOR data3 XOR data4) ? or use h(data1||data2||data3||data4)?
3
votes
1answer
176 views

Updating stored, encrypted containers on a server

My scenario is this -- I want to store an encrypted container on a network server. This encrypted container should be accessible to others to download and decrypt/mount locally provided they have the ...
5
votes
1answer
173 views

Detecting PRNG Use from Output

Question: Is there a way to detect the use of a PRNG strictly from observing the output provided by an application? Background: During an audit of a key generating algorithm that I knew was based on ...
3
votes
1answer
354 views

Kerberos realm understanding

Could someone summarise why realms are necessary in Kerberos and the advantages of the concept. I'm struggling to isolate everything I know / beginning to understand into some well defined points for ...
4
votes
3answers
2k views

Is a 512 bit RSA key secure when used temporary?

Is a 512 bit RSA key secure when a new key gets generated and used approximately once a week? The key is only used for signing messages, not for encrypting sensitive data. This is for a system where ...
1
vote
2answers
413 views

Can I use hardware token OTP to stop piracy?

Our firm sells an offline desktop (.exe) software, we are thinking of using OTP (from hardware token like in internet banking) to stop people from copying the software without permission. Basically, ...
5
votes
2answers
3k views

how strong is AES without salt

The AES cryto library provided to us from company, does not generate a different encrypted value for plain text. If text is "abcd" , it will generate the same encrypted value over multiple ...
1
vote
1answer
532 views

Storing Private Keys Generated on Server with specific User's Password Securely

I am currently building a system (PHP Web Application Framework) that creates an RSA Key Pair for a user to allow other users to send secure information from one to another. The public key is ...
5
votes
1answer
579 views

Can I re-use another vendor's dual factor token in my own system? (Avoid physical token bloat)

I read the open source multifactor authentication techniques called HOTP RFC 4226 and TOTP RFC 6238 and realized that a single random number is the basis for the token's cryptography... and that this ...
19
votes
2answers
41k views

Security comparsion of 3DES and AES

Which one is more secure and least possible to be broken through cryptanalysis AES or 3DES (no matter performance)? I need to use encryption for my projects to store and secure sensitive information ...
2
votes
1answer
737 views

How does the YubiKey Validation Server work from an encryption perspective?

Many YubiKey servers rely on the free cloud hosted authentication that comes with the product, but I'm interested in keeping all cryptographic material in my control. For that reason I am looking at ...
4
votes
1answer
233 views

Combining MAC and Encryption

What is the most preferred and secure way of combining both Encryption and MAC. There was a lecture on different combining strategies adopted by different protocols on a cryptography course by ...
5
votes
1answer
2k views

OpenVPN Why CBC mode is recommended?

I just set up my installation of OpenVPN on my server. I am curious why the OpenVPN manual recommends CBC mode. I heard that CBC is predictable and not secure; is that true?
1
vote
1answer
125 views

Reasonable computationally lightweight security?

I've read a bunch about how one should use bcrypt or PBKDF2 as a good middle ground between tunable workload and acceptable time to make brute force and collision attacks unfeasible. What if the ...
23
votes
7answers
1k views

At what level of abstraction should a developer work with with regards to cryptography?

I have recently came across an old blog post by Jeff Atwood which got me thinking. What could be easier than a EncryptStringForBrowser() method which has security and tamper-resistance built in, ...
3
votes
0answers
68 views

Is the use of JavaScript for cryptography ever appropriate in the browser? [duplicate]

Possible Duplicate: How secure is aSSL (javascript)? Does it effectively mimic SSL? After some searching around, I realized we don't have an easily visible canonical question about this on ...
2
votes
3answers
3k views

KDC(Key Distribution Center) vs Asymmetric Key Exchange

Today I was reading notes about cryptography and I came across a problem that exists in Symmetric Key encryption, which is how to share the secret key across the network. 1st Method : Make use of ...
3
votes
2answers
1k views

What hardware technology (GPU, FPGA) is fastest at generating RSA keys?

I'm interested in generating RSA keys in rapid succession and am looking for the correct hardware to so. I think what I'm looking for is very similar to a brute force attack on RSA keys, but my ...
164
votes
8answers
73k views

Why not use larger cipher keys?

RSA Security commonly uses keys of sizes 1024-bit, 2048-bit or even 3072-bit. And most Symmetric algorithms only between 112-bit and 256-bit. I do realize that the current keys are secure enough for ...
22
votes
7answers
6k views

Why don't people hash and salt usernames before storing them

Everyone knows that if they have a system that requires a password to log in, they should be storing a hashed & salted copy of the required password, rather than the password in plaintext. What I ...
4
votes
3answers
659 views

Impact of Quantum Computers, other than new algorithms

When large scale quantum computers come along, algorithms based off of the new principles will have an impact on how we encrypt data, with Shor's algorithm rendering RSA vulnerable and Grover's ...
16
votes
5answers
1k views

Rainbow table concept for Prime numbers

Is there a concept where pre-computed tables can be used for prime number factorization ? Is it possible that a computer can generate millions of prime numbers, store it and then effectively determine ...
0
votes
1answer
1k views

ECDH is better than plain RSA? [closed]

RSALabs recommend using at least 4096 bit long RSA keys to encrypt emails but we have some performance difficulty with 4096 RSA. my noob question is what is ECDH (i didn't understood from wikipedia ...