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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Certificate authorities for a PKI

Some people think the certificate authorities for a PKI should be the government, but others think certificate authorities should be private entities, such as banks, corporations, or schools. What are ...
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850 views

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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Is there a way to accept signed requests without storing client's password in plaintext?

We are developing REST Web service. We will give Identifier and Secret string to each of our REST clients. When doing requests, clients will authenticate themselves using HMAC algorithm (they will ...
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Compute the AES-encryption key given the plaintext and its ciphertext?

I'm tasked with creating database tables in Oracle which contain encrypted strings (i.e., the columns are RAW). The strings are encrypted by the application (using AES, 128-bit key) and stored in ...
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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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2answers
570 views

Is a large number of RSA-encrypted files a vulnerability?

Would having a large number (10^4) of RSA encrypted files make it easier for an attacker to find my private RSA key? Update: These files would be available to the attacker, and perhaps the content of ...
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1answer
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TLS replay attack - requirements of the serverHello nonce

As you all know, the SSL/TLS protocol requires both client and server to exchange (in clear text) a random number or nonce. This is presumably used to prevent replay attacks. It is not clear to me ...
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Should RSA public exponent be only in {3, 5, 17, 257 or 65537} due to security considerations?

In my project I'm using the value of public exponent of 4451h. I thought it's safe and ok until I started to use one commercial RSA encryption library. If I use this exponent with this library, it ...
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2answers
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What are the differences between MD5, SHA and RSA?

MD5 tools output hexadecimal values. In the same manner, do SHA and RSA together produce a hexadecimal (or any other) output? What are the differences between the MD5, SHA and RSA algorithms?
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MD5 display format

When I run MD5 algorithm I am getting an output in numeric and a few lower case letters. Obviously it uses all numeric digits and rarely i saw some lower case alphabet letter. I need to understand ...
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How can I mitigate the threat that DPAPick poses to my DPAPI protected data?

The Windows Data Protection API (DPAPI) is the suggested method for storing secrets on Windows systems (such as database passwords required by ASP.Net applications). DPAPick was presented at BlackHat ...
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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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5answers
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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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387 views

What can one do when encryption methods fail?

I'm in search of an expert to answer my curiosity. Suppose that methods like AES/DES, SSH, PGP, RSA, etc. can be cracked or fail somehow. In other words, suppose that it's possible to determine one ...
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6answers
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Is PBKDF2-based System.Cryptology.RFC2898DeriveBytes() “better” for Unicode Password hashing than traditional methods?

When is it appropriate to use RFC2898DeriveBytes versus a typical hash? Update I now understand that a KDF is typically used to create a symmetric key for possible use in encrypting a stream. I ...
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1answer
218 views

What is encryption method for the 3rd part of the Kryptos text?

http://fr.wikipedia.org/wiki/Kryptos_%28sculpture%29 http://en.wikipedia.org/wiki/Kryptos I read the Kryptos wikipedia page, is says it's crypted with a "modular transposition of lines and columns". ...
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How long should a random nonce be?

NIST provides good guidelines on the length of keys and hashes for various algorithms. But I don't see anything specifically on the length of a random or pseudo-random nonce (number used once). If ...
9
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458 views

Are there any smartcard/hardware-tokens for certificate-based authentication which are easily destroyed?

It's all very well to use multi-factor authentication, but supposing you want to 'destroy a factor' so that in an situation where you are likely to be coerced to provide your passphrase, you can ...
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2answers
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Classical Cryptography Tools

I'm wondering if there are any tools out there that can assist in solving classical cipher text. I'm looking into developing some tools such as frequency analysis, transposition tools and so on but ...
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Why triple DES used in EDE mode?

Why is triple DES is calculated in encrypt decrypt encrypt mode? Why a decrypt in the middle? And isn't decrypt = encrypt since DES in a symmetric cipher?
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4answers
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Initialization vector with cipher block

Is the initialization vector used to encrypt a block of data always static or dynamic? If it is dynamic then I should send the IV along with the key to the recipient right? This normally doesn't ...
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4answers
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What type of cipher is RSA?

Is RSA a stream cipher or a block cipher?
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2answers
2k views

where can find sample coding for use of Bouncy Castle(java)?

I had found bcprov-ext-jdk16-145.jar and bcprov-jdk16-145.zip. I wish to use the IDEA encryption to encrypt XML, but i haven't found any sample of coding in JAVA. Can anyone tell me how to call the ...
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2answers
756 views

What kind of encryption is a one-time pad?

Is it a substitution cipher or a stream cipher or both?
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3answers
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Whats the difference between MAC vs hash

What is the difference between the two algorithms? One difference that I know of, is that MAC is keyed and hash is not.
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239 views

Renew digital certificate

If I have deployed a digital certificate on a webserver and if it needs to be renewed then what steps do I need to follow? Will I need to generate a new longer public key private key pair? Why do ...
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542 views

Personal digital certificate how to verify

A server certificate would have its domain name at its subject field. A personal certificate would have your name as the subject field. How can you be sure that there are no two certificates with the ...
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Certificate chain

For my computer to verify the identity of a certain certificate should it have all the certificates up to the root certificate?
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SSL Certificate revocation check

In the SSL protocol I don't see where the certificate is checked for revocation status. https://developer.mozilla.org/en/Introduction_to_SSL Is the Certificate Revocation and Status Checking not ...
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3 way authentication

Can someone please tell me what does 3 way authentication mean? I cannot understand this concept? :( Now if there are two people A and B 1.) A challenges B with a question 2.) B gives the answer and ...
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1answer
119 views

Protect file in a web site

How would you protect a password file in a web site? Is hashing the individual passwords not enough? What other steps do I need to follow?
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Encryption decryption time

Does the encryption / decryption time of rsa algorithm vary significantly with a change in key length? For example, is there a noticeable difference in encryption/decryption time between 512 bit and ...
4
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1answer
187 views

When does one need to be concerned with leaking timing information in .NET?

According to this post, Dominick Baier was comparing two HMACSHA256 signatures and was leaking timing information upon an unsuccessful comparison. When working with .NET crypto classes, when should ...
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2answers
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What is an intermediate certificate authority?

What is meant by an "intermediate certificate authority?"
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1answer
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Is SSL key generation client-side, server-side, or both?

Who generates the session keys for a SSL symmetric encryption? Is it the client for both client and server where client generates part of it while the server generates the other part?
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Why should one not use the same asymmetric key for encryption as they do for signing?

In an answer to a question about RSA and PGP, PulpSpy noted this: It is possible to generate an RSA key pair using GPG (for both encryption and signing -- you should not use the same key for ...
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3answers
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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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2answers
149 views

What are the advantages of sequential signing

What the advantage of sequentialy signing a document? That means signing a document by two people in a sequential manner?
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4answers
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How to achieve non-repudiation?

If I have a message that I need to send to another person, how do I achieve non repudiation ? Is digitally signing the message sufficient ?
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3answers
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How can I enumerate all the saved RSA keys in the Microsoft CSP?

I have an application that is creating several keys and storing them in various stores (in this case the Machine store). How can I enumerate all the keys on a given Windows system? ...
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votes
1answer
668 views

Why does Bouncy Castle have a separate download for the IDEA algorithm?

I'm looking at downloading the C# binary for Bouncy Castle and see two downloads with source code. One has the IDEA algorithm, the others presumably not. http://www.bouncycastle.org/csharp/ Why ...
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7answers
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What are the realistic, and most secure crypto for Symmetric, Asymmetric, Hash, Message Authentication Code ciphers?

I'm interested in updating this two pronged question for 2011: What cryptology is most appropriate for low-powered devices (such as a cellphone), and yet still effective? What cryptology is most ...
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2answers
6k views

How does RSA encryption compare to PGP?

On this answer ck says RSA and PGP are different. What you are essentially asking is how do I run my petrol car on diesel? The answer is you can't. I would be interested in a more ...
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1answer
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How do I use C# to encrypt/decrypt data where the private key is on a smartcard, hardware security module, TPM chip etc

Is anyone aware of a C# code sample to interact with smartcard, hardware security module, TPM chips (etc), that will allow me to encrypt and decrypt data? My goal is to allow my application to ...
26
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8answers
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If someone breaks encryption, how do they know they're successful?

Let's say I have a file containing a random bunch of bits and then I encrypt it using some modern algorithm (Blowfish, AES, or whatever). If someone captures the file and mounts a brute force attack ...
6
votes
2answers
484 views

How can I authenticate a client connection in a secure way?

Let's say I have a server listening on port 1234. I have some client software that needs to be able to connect to this port. But I want to prevent malicious users from bypassing the client software ...
52
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5answers
47k views

What is the difference between SSL vs SSH? Which is more secure?

What is the difference between SSH and SSL? Which one is more secure, if you can compare them together? Which has more potential vulnerabilities?
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1answer
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What are the problems with encrypted but unsigned data?

In another question's answer, D.W. wrote: Make sure there is authenticity protection for the encrypted data (e.g., encrypt and then sign/MAC): you will need both confidentiality and authenticity ...
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2answers
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3DES vs DES for VPN connections

I'm trying to get Android 2.1 phones to connect to our corporate VPN, but it would appear they only support DES rather than 3DES for encryption. Is it safe to use DES, am I going to get hacked if I ...
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What common products use Public-key cryptography?

I want know what common use products are there that use public key/private key cryptography?