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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Describe an example of indistinguishability obfuscation or functional encryption

As described in Perfecting the Art of Sensible Nonsense, a major breakthrough in cryptography research was published in the summer of 2013: Candidate Indistinguishability Obfuscation and Functional ...
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Securing a prediction about a future event

I want to make a prediction about a future event, but only reveal that prediction after the event occurs lest knowledge of my prediction affect the outcome. For example, suppose Alice predicts that ...
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Why do PGP master keys only have a single subkey, and tie certification with signing by default?

After learning more about PGP subkeys and how to split apart the roles of (S)igning, (E)ncryption, (A)uthentication and (C)ertification, I discovered that in most cases(?) a default master key has a ...
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Question about dictionary attacks on GnuPG symmetric encryption

They say algorithms like AES can't practically be broken given a long enough key length (> 128 bits). If I use GnuPG to encrypt a file using AES: gpg -c --cipher-algo AES secretfile it asks me for a ...
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Key management in cloud datacenters

In terms of infrastructure, how do Cloud providers (organizations providing SaaS, PaaS, or IaaS via the cloud) manage keys and cryptography? From my understanding, "private" datacenters tend to ...
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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 ...
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Question of importance of FIPS in security implementations

I am by far, no security expert but I experience on the subject working in Java (JCA,JCE and JSSE). Anyway, recently there was a discussion about FIPS compliance. I looked into this and SUN's ...
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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 ...
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Do mobile OS's provide crypto-quality randomness?

Which mobile OS's provide a primitive to generate crypto-quality randomness that applications can use? On desktop systems, these features are pervasive. Unix provides /dev/urandom. Windows provides ...
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Security of using passwords or even passphrases to encrypt files

Is it ever appropriate to use real-world passwords to encrypt files to be sent via unsecure means. By real world, I mean a password that is memorable and memorisable by a mere person? I am implying ...
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License key / Serial number generator and checker

I need a serial number generator and accompanying checker. I would like to be able to set a salt (and maybe a length). The generator should only produce serial numbers that pass the test of the ...
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Using computer random number generators to produce keys, it is secure?

Does generating an encryption key using the random number generator on one's computer present a security risk? If so how might that risk be mitigated, specifically when generating RSA key pairs in ...
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What is the benefit with using encrypted RAM Memory?

I sometimes hear that encryption is used for the RAM Memory, but I don't really understand why this is needed. Why is RAM Memory needed to be encrypted? and is this done by the hardware, the ...
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What kinds of SSL certificates are usable for encryption?

I know that Verizon SSL certificates cost close to $600. There are couple of cheap alternatives, but I never really understood why Verizon does not offer such certificates. Look for RapidSSL at ...
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Why isn't OCSP required by default in browsers?

According to the following screenshot, taken from firefox-3.6.17-1.fc14.i686, Firefox has an option to fail closed when unable to connect to OCSP servers. Can someone please explain why this isn't ...
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Can RSA keys be swapped?

On a theoretical level, is there anything inherently different about public vs private keys? During RSA key generation there are two keys generated, key A and key B. Key A is private and Key B is ...
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Why can an encrypted private key be brute forced?

When using SSH keys to authenticate to a server for remote access, why is it possible to devise the true key and therefore the passphrase from an encrypted private key, without checking each guess of ...
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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 ...
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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 ...
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How to exchange RSA public keys safely between two parties?

How to exchange RSA public keys safely between two parties via internet?
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Is there a length beyond which increasing password length provides no additional security?

Assuming that the password is stored hashed and salted, and that it is a string of random characters, is there a point where adding to password length doesn't add security? Since the hash will have a ...
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Multiple CAs signing a single Cert/CSR?

Just saw this suggested on Slashdot So I've seen quite a few people wanting a switch to self-signed certs (who IMO mostly don't understand what making that secure actually involves), and an idea ...
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Is there an organization that reviews/approves crypto implementations?

As I understand it, NIST approves crypto algorithms but doesn't cover specific implementations. I think I've read about IEEE approving hardware implementations of, e.g. AES, but I can't think of any ...
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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 ...
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Additional security of keyfile on top of a master password for KeePass

I use KeePass + Dropbox to manage and synchronize my passwords across my devices. This system works really great and I trust KeePass' security model. However my biggest remaining concern is the ...
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Strength and length of Symmetric vs Asymmetric keys [duplicate]

There are many questions surrounding the differences between symmetric and asymmetric encryption keys. I think I've read them all at this point. But I'm still left wondering: Why does a "secure" ...
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Whenever an unhandled exception somehow makes it into production, is it safe, viable, etc. to print an encrypted stack trace to the end user?

Whenever an unhandled exception makes it into production somehow - whatever the reason - there's generally an option (especially with .NET programs) to print out a stack trace to the end user before ...
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Security of SHA256 and Bitcoins

The Bitcoin network use SHA256 as a core component to it's design. I'm no expert on cryptography, but it seems to me it usually is only a matter of time before security vulnerabilities are discovered ...
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How can I audit which type of Block Mode encryption is being used when no source code is available?

Given that there are clear advantages to using some block modes of encryption over another, and I would like to ensure that all software used in the enterprise uses a certain "level" of security I'd ...
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How does an SSL server prove its identity?

This document says that a challenge response authentication proves the servers identity. But is a man in the middle attack still possible if the client does not verify domain name ? Please help me ...
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Should we configure all devices to never request SSL 2.0, and reject it if offered?

In an effort to reduce man in the middle attacks, when will it be (or was it) an industry accepted practice to reject SSL 2.0 connections on the client and server side? Is configuring this on a proxy ...
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532 views

has scrypt withstood the test of time?

I've always heard that scrypt was better than bcrpyt... because of memory causing GPU a very difficult time to crack. However, the notion always was that scrypt hadn't been tested, it was kind of a ...
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SSL handshake failure modes

In SSL if the handshake is not succesful, does it always end with a handshake alert? Or are there other ways to finish the SSL connection (acceptable by standard). I am asking this, because in an ...
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Are there really functioning quantum computers?

I saw this video on youtube on quantum computing. It says that a company called dwavesys has already made commercially available quantum computer. I checked on the website and it exists. I thought ...
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What does “key with length of x bits” mean?

I'd like to know what it means to say "the cryptosystem C uses keys with a length of x bits". I do not understand what the bits length means... doesn't it depend on the encoding? The same word encodes ...
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Forward secrecy for kids

In the Scouts, it is popular to use secret codes to write messages (which are simple ciphers). I want to introduce Forward secrecy to the kids so they can use it with these ciphers. So, if the ...
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How does a weakness in a random number generator lead to a compromise of the entire cryptographic process?

In the news, there are several articles (here, here, and the technical point of view) which have to do with a weakness in a random number generator. The question is somewhat twofold. What symptoms do ...
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Cryptographic Security of Dynamically Generated, Non-Random Salts

So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
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How much security is compromised if we accept other characters as login (other than the original password)?

I've just realised that facebook accepts 3 forms of a password: Source: Facebook actually accepts three forms of your password: Your original password. Your original password with the ...
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How does the padding scheme impact the security of encryption

After digging a little deeper into cryptography I am wondering what impact the different padding schemes do have an the security of an encryption algorithm. Lets take AES-128 in CBC mode as an ...
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Location to store an encryption key

I'm building a secure system which stores messages on a server in a Postgresql database. The messages are stored encrypted with PHP's openssl_encrypt() function with the AES-256-CBC method. At the ...
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What was SSL 1.0?

What was SSL 1.0? SSL 2.0 and 3.0 are well-known and well-documented. But what did the SSL 1.0 protocol look like? Wikipedia says there was a SSL 1.0 but doesn't say anything about how it worked. ...
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In the recent DKIM vulnerability, how did someone determine key length by looking at headers?

Having read this recent article : Wired-DKIM vulnerability, I have a couple of questions. How can one determine the key length that is being used simply by looking at the headers ? And I'm assuming ...
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Tool for public key cryptography where password is the private key?

Is there any free & open source tool for public key cryptography, where the private key is just a chosen password? Here is what I need: I want to make backups every hour using a script I want ...
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4096 bit RSA encryption keys vs 2048

Where do 4096 bit RSA keys for SSL certs currently stand in terms of things like CA support, browser support, etc? In the overall scheme of things is the increased security worth the risk of 4096 bit ...
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How to get a 'million rounds of PKCS#8 + PBKDF2' with OpenSSL?

I posted this question Is a passphrase-protected SSH private key susceptible to a dictionary attack? a few days back. An excerpt from the final answer: With PKCS#8 + PBKDF2 and one million ...
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Suitable cipher for SMS encryption

I would like to create application for encrypting SMS messages. After long enough discussions I decided to use symmetric encryption, since handling public/private keys issue is too difficult for most ...
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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 ...
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What are the practical uses of large asymmetric keys?

The Windows CNG supports keys of varying sizes, e.g. RSA up to 16384 bits: http://msdn.microsoft.com/en-us/library/windows/desktop/bb204778(v=vs.85).aspx. My understanding is that in crypto today we ...
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Is it preferable to perform encryption using database functions or code?

Several databases I am familiar with provide functions or modules for encryption. Examples include dbms_crypto for oracle databases and built-in functions for MySQL. Most of the commonly used ...