Questions tagged [.net]

A runtime, architecture, and libraries for Microsoft Windows used for creating applications.

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68
votes
21answers
58k 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 ...
8
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3answers
41k views

How can I detect a VPN connection (even just in some cases) to get the real location of the user

I'm creating a web site, I would like to allow people to sign-up only from their "real" physical location (not using a VPN). I was thinking maybe comparing local and server time... what else...? ...
7
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3answers
5k views

Reference implementation of C# password hashing and verification

Does anyone have a reference implementation (ideally 3rd party certified, or government approved) way one-way hash a password for C# and or Java? Ideally,I'd like to see something that includes a "...
15
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6answers
10k views

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 ...
33
votes
3answers
7k views

Is using the username encrypted with the password as key a good password storage scheme?

On web applications I build I don't hash the passwords. Instead I symmetrically encrypt the username using the user's password and store the result in the password field. I use RijndaelManaged on ...
3
votes
1answer
2k views

Using GPG or PGP for symmetric database encryption/decryption in c#

I am looking to symmetrically encrypt/decrypt information in a database. This info consists of short pieces of information, which need to be individually encrypted when a specific method is called. I ...
1
vote
1answer
662 views

What does “don't roll your own security” mean?

I see this saying a lot and agree that you should leave certain things to the tried and true methods, but am unsure to what extent. Does it just mean don't make your own crypto algorithm? I created a ...
49
votes
4answers
13k views

How to approach replacing md5 for transporting Unity game data to a remote server

TL;DR I am working on a gaming system that uses UnityScript and C# on the client and PHP on the server. A MD5 hash of the data plus a shared secret is used to check that the data has not been ...
23
votes
7answers
27k 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 ...
9
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4answers
3k views

What Partial Homomorphic Encryption implementations exist and how do I leverage them?

It appears that only Partial Homomorphic Encryption(P.H.E.) is practical for modern day (2011) use. However I'm having difficulty locating libraries (FOSS or otherwise) that enable me to leverage ...
21
votes
1answer
7k views

Is Rfc2898DeriveBytes using HMAC SHA1 still considered “secure enough” for hashing passwords?

I've been told by a CISSP that the .NET class Rfc2898DeriveBytes would not pass a security audit today because it still uses SHA1. It's reliance on SHA1 - even with the iterations - leaves it too ...
7
votes
3answers
13k views

How to bypass .Net 4.5 request validation, for an XSS attack?

.Net has a feature called request validation which detects malicious inputs and blocks the request. By its nature, request validation is not a precise science. OWASP clearly recommend to only rely on ...
5
votes
2answers
1k views

In Visual Studio, what are the risks of simply opening an untrusted project? What are the mitigations?

I'm looking at the source code of some potentially hostile code. As usual, VS 2012 is giving me the security warning: "You should only open projects from a trustworthy source" ... "ask me for every ...
11
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2answers
4k views

Data Encryption and Key Management in C#

Which route to take, what are the pros and cons, which is more secure.. Generate AES key, encrypt the data with it and then encrypt the AES key with RSA, save the encrypted data and encrypted AES key ...
5
votes
1answer
350 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 ...
1
vote
5answers
216 views

Potential Risks Using Reference Code Based Authentication For Web Based Application Form That Contains SSN

I'm currently building a web based membership application form that will require a user to enter an SSN and other identifiable information. Part of the requirements of the membership application is to ...
13
votes
5answers
7k views

Is it safe to binary-deserialize user-provided data?

AppHarbor has a blog post containing sample C# code which reads data from an unsigned cookie and passes it through .Net binary serialization. Is that safe? Obviously, the data is completely ...
26
votes
11answers
8k views

Is obfuscation worth it [closed]

There are many tools to obfuscate .NET applications. The free ones do some basic obfuscation while commercial ones seem to promise more. My question is: Is it worth to use the commercial obfuscation ...
9
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2answers
4k views

Is it a security risk to maintain an application developed for a version of .NET prior to 4.0?

I've had a request that we upgrade all our internally developed applications to .NET v4.0. Needless to say, this is a massive chunk of work. Is using applications based on the .NET framework prior to ...
7
votes
1answer
511 views

Are there any type safe languages with deterministic compilers?

This article about BIND9 concludes with the statement: The point I'm trying to make here is that BIND9 should not be exposed to the public. It has code problems that should be unacceptable in this ...
4
votes
1answer
6k 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 ...
3
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3answers
2k views

AES for key encryption

Is AES a good choice for protecting a key stored on the computer of a user of my application? I have seen threads on hashing passwords that suggest using slow algorithms for defending against brute ...
1
vote
1answer
117 views

When calling a process from another process, Is sending stdin password more secure than sending an ENV variable?

I am a Java developer that is building an app where it needs to call a C# process from within. In my situation, the Java app is calling this C# program https://github.com/nddipiazza/...
1
vote
2answers
586 views

How to securely send a password from one app to another app?

See this question/answer first: When calling a process from another process, Is sending stdin password more secure than sending an ENV variable? I am a Java developer that is building an app where ...
11
votes
4answers
3k views

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 ....
7
votes
2answers
5k views

C# Image.FromStream is that secure?

after reading the data from the request as Stream i needed to convert it to Image so i used this Method: Stream inputStream = HttpContext.Current.Request.InputStream; Image img = Image.FromStream(...
3
votes
2answers
303 views

Security concerns with a “fiddle” site?

I recently came across a cool site for testing .NET code (http://dotnetfiddle.net/). In the FAQs they mention that they have two restrictions for security purposes: No access to File System IO No ...
2
votes
2answers
263 views

Keyed-hashing a password with a hash of the password + salt as the key, is it safe?

I was looking at our authentication system which hashes passwords differently than I was taught. The salt is a constant byte array and it uses the password + the salt as a key for the password hashing ...
6
votes
1answer
2k views

Secure query string parameters

I have an application which use the Thick box jQuery component to open a popup page . And I pass my parameters in query string like this : <a id="btnShowPopup6" runat="server" class="thickbox" ...
5
votes
1answer
241 views

Does every security patch get back ported to every .NET framework? Are there exceptions to the rule?

I can imagine a scenario where Microsoft will create a security patch for some versions of .NET and not others. This might occur in occasions it's too expensive to regression test and back port all ...
4
votes
2answers
7k views

Ways to inject malicious DLLs to exe file and run it

I'm trying to find all vulnerabilities in my given system. Assume a malicious user has the executable (.exe file) of my .NET application (C#), and a malicious DLL he or she created. Can the DLL be ...
4
votes
1answer
1k views

Peer review of C# cryptography for Azure Table security

Edit: Update - I am researching how to implement AES with authentication in an efficient way for this project. If you have the time I'd appreciate your skill in finding the best implementation for ...
3
votes
1answer
2k views

How does RSACryptoServiceProvider generate keys

The documentation for the constructor for RSACryptoServiceProvider states "If no default key is found, a new key is created. This constructor creates an Exchange key pair suitable to encrypt session ...
2
votes
3answers
2k views

Securely store basic auth credentials in database

I need to be able to communicate with a REST API Service and store the username/password pair in a database. The client talks to the API from a server within our DMZ, but gets the credentials from a ...
1
vote
2answers
2k views

When should one use RSACryptoServiceProvider vs AESCryptoServiceProvider

I am interested in storing certificates for various purposes on a SmartCard. Since this answer illustrates how there are confusing differences and similarities between RSA and AES When should one ...
1
vote
3answers
381 views

How can I add a layer of security to cleartext passwords and SSL?

I'm creating a web API in .Net for a web application. I'm wondering what the industry standard for login authentication is. I know that most people believe that sending cleartext username/passwords ...
-1
votes
1answer
494 views

How to encrypt files without giving the user access? [duplicate]

I don't know if I should ask this question on security.SE or stackoverflow, so please move my post if necessary. I want to store my (C#) application data in a way that the user cannot read or modify ...