Questions tagged [.net]

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

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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 ...
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10 votes
3 answers
51k 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...? ...
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7 votes
3 answers
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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 "...
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2 votes
1 answer
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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 ...
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15 votes
6 answers
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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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33 votes
3 answers
8k 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 ...
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4 votes
1 answer
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 ...
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91 votes
6 answers
131k views

Best place to store authentication tokens client side

When my users are authenticated they receive an authentication token, I need to use this authentication token to authorize some asp.net WebAPI calls. To do this I need to add the token to the head of ...
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50 votes
4 answers
14k 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 ...
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24 votes
7 answers
29k 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 ...
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28 votes
10 answers
12k 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 ...
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22 votes
1 answer
10k 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 ...
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9 votes
4 answers
4k 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 ...
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8 votes
3 answers
24k 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 ...
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7 votes
2 answers
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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 ...
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11 votes
2 answers
5k 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 ...
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6 votes
1 answer
422 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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1 vote
5 answers
313 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 ...
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15 votes
5 answers
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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 ...
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9 votes
2 answers
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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 ...
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8 votes
1 answer
651 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 ...
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4 votes
2 answers
402 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 ...
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4 votes
1 answer
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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 ...
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3 votes
3 answers
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 ...
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  • 601
1 vote
1 answer
233 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/...
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1 vote
2 answers
1k 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 ...
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11 votes
4 answers
4k 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 ....
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9 votes
2 answers
6k 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(...
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  • 191
5 votes
2 answers
9k 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 ...
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2 votes
2 answers
360 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 ...
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0 votes
1 answer
1k views

Encrypt and decrypt large files with RSA, is it possible? [closed]

Encrypt and decrypt large files with RSA, is it possible? I need to encrypt / decrypt files and save the private key named file encoder I've seen it's not acceptable to work on large files with RSA Is ...
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7 votes
2 answers
6k views

How to securely use Process.Start?

I am using Process.Start in a Windows Service I created to execute an exe that I have on my server that is used for audio conversion. I am passing some user input as a parameter to this exe. The ...
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6 votes
1 answer
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" ...
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5 votes
1 answer
298 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 ...
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4 votes
1 answer
3k views

What do you search for in Open Source code to be sure there isn't malicious code?

I realize the answers will be language specific, but I am curious what terms you would look for when checking something out on Github? I was looking for a remote administration tool that I could use ...
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4 votes
1 answer
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 ...
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3 votes
1 answer
3k 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 ...
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  • 179
3 votes
3 answers
3k 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 ...
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1 vote
2 answers
3k 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 ...
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1 vote
3 answers
428 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 ...
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0 votes
2 answers
217 views

How do I do asymmetric/hybrid encryption in practice?

Question I would like to asymmetrically encrypt messages with a public key that I have been given in advance. How can I go about doing that? Some example code in C# would be much appreciated. What do ...
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  • 175
-1 votes
1 answer
555 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 ...
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