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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Should the bit-strength selection of a child certificate be influenced by the CA or the chain?
All things being equal; suppose I have a CA chain that has 1024 bits of RSA encryption. Does this mean that my selection of a child CA or WebServer certificate gains no benefit from a higher level of ...
5
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3answers
3k views
What SSL key should I make for IIS: RSA or DH? What bit length is appropriate?
I'm creating an SSL cert for my IIS server and need to know when I should choose the Microsoft RSA SChannel Cryptographic Provider or the Microsoft DH SChannel Cryptographic Provider.
Question 1 Why ...
3
votes
4answers
320 views
Generating OpenPGP key pair with restrictions
I intend to generate an OpenPGP RSA key pair where a part (~half) of the private key is as I specify, i.e. a specific string. Are there tools for generating a key pair with such restrictions, or will ...
7
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3answers
1k views
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 ...
10
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3answers
574 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 ...
4
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3answers
563 views
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 ...
8
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5answers
7k views
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 ...
6
votes
4answers
4k views
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 ...
11
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2answers
413 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 ...
9
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1answer
1k views
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 ...
14
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5answers
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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 ...
10
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2answers
6k views
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?
3
votes
2answers
240 views
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 ...
8
votes
3answers
812 views
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 ...
68
votes
20answers
16k views
Lessons learned and misconceptions regarding encryption and cryptology
Cryptology is such a broad subject that even experienced coders will almost always make mistakes the first few times around. However encryption is such an important topic, often we can't afford to ...
9
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3answers
1k views
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 ...
10
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5answers
1k views
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 ...
8
votes
5answers
338 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 ...
10
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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 ...
3
votes
1answer
167 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".
...
13
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3answers
2k views
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 ...
8
votes
3answers
340 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 ...
7
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2answers
734 views
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 ...
6
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3answers
4k views
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?
6
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3answers
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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 ...
5
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2answers
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2answers
947 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 ...
4
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2answers
604 views
8
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3answers
4k views
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.
6
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3answers
188 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 ...
6
votes
3answers
424 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 ...
6
votes
3answers
923 views
Certificate chain
For my computer to verify the identity of a certain certificate should it have all the certificates up to the root certificate?
8
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2answers
2k views
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 ...
0
votes
3answers
1k views
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 ...
3
votes
1answer
112 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?
7
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2answers
2k views
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 ...
3
votes
1answer
153 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 ...
2
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2answers
1k views
What is an intermediate certificate authority?
What is meant by an "intermediate certificate authority?"
6
votes
1answer
1k views
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?
18
votes
3answers
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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 ...
8
votes
3answers
750 views
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 ...
2
votes
2answers
134 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?
21
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4answers
5k views
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 ?
6
votes
1answer
2k views
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?
...
4
votes
1answer
504 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 ...
10
votes
7answers
3k views
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 ...
11
votes
2answers
2k 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 ...
3
votes
1answer
2k views
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 ...
24
votes
8answers
1k views
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 ...
5
votes
2answers
332 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 ...
