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How to setup TLS-SRP protocol on client and WebAPI REST server

I would like to use the TLS-SRP protocol to secure the communication between a mobile app client and a WebAPI REST server. My primary reason is to avoid using self-signed certificate stored on the device or hardcoded for security reason (breach, decompiling...). Setting up the salt between the server and the client is not an issue. However I don't know how to customise the HttpClient on the client-side and the WebAPI server to follow the protocol.
Has anyone done that before? Could you point me to any documentation?
Cheers,

Use encrypted connection on mySQL server[C#]

I created a chat recently on C#. What it does is that uses mySQL parameterized queries to upload the message from the user to the server. Then the other clients download this message to their "screen".
Now my question is this. Do i have to use SSL to encrypt the connection ? And if yes, how i can do that ? Everything i found online is completely confusing for me...

You can do encryption in your app one (or both) levels:
Transport layer: by using SSL (HTTPS): this is easy to do and ready-made. See this, for example.
Application layer: you encrypt your messages in your application manually using some library, and you send the messages encrypted (to the database or the other client). There are a lot of possibilities here (algorithm, library, ...)
You can do both: crypt your messages manually and send them using SSL.

How to create a stateful encrypted connection between two C# applications?

I am currently looking for the best way to establish a stateful and encrypted connection between a C# client and server application. First, I thought about using IPsec, but as it works on a low level (OSI: Internet Layer), I would be very hard to implement, if you want the functionality inside your program and don't want to rely on the OS.
What technologies would you recommend for this purpose? Is there some functionality already built into .NET (4.5)? It does not neccessarily have to be stateful, working with some kind of heartbeat would be a valid option, too.

You'll want to use a standard protocol such as SSL rather than trying to make your own. First the implementation will be much easier because the .NET framework will support it, and the transport protocol that runs underneath it is stateful (e.g. TCP). Second developing a cryptographic protocol that is secure is very difficult, and SSL has already been implemented so why reinvent the wheel?
SSL works by using PKI (Public Key Infrastructure) to generate a shared symmetric key. The handshake consists of a number of steps. First the client sends a request for a secure session, then the server responds with it's certificate, the client verifies the certificate by crawling up the ladder through the certificate authorities (e.g. Verisign, Thawte, GeoTrust etc...) or if it already trusts the server it can just accept the certificate that is self signed.... and once it finds the certificate is trustworthy it generates a symmetric key and picks an algorithm (e.g. AES, 3DES, RC4, IDEA etc...). The client then encrypts the key and algorithm being used with the public key, then the client sends that value to the server and a secure session can proceed using symmetric encryption which is much faster.
SSL itself is can be used in a stateful manner because it actually works over the transport layer in the OSI Model, HTTPS on the other hand is not a stateful protocol by design. HTTPS is HTTP over SSL so the two technically don't really have anything to do with each other, except that in HTTPS SSL is used to secure the application data that is being requested. With HTTPS as with HTTP once a request is made to the server it basically forgets about you (not exactly how it happens but for all intents and purposes you can think of it this way). I myself would prefer the use of HTTPS if you can get around having to have a stateful protocol. The main reason for doing so is so that I wouldn't have to write the code and possibly have a mistake in the implementation of SSL. All you have to do is build a WCF or REST based service that runs on IIS and get a certificate for your server.
That being said, if you still want to create your own SSL server that doesn't use HTTP on the application level you can use the TcpListener and TcpClient classes along with the SslStream class provided as part of .NET to create your own. MSDN has a good example of how to create an SSL server and client: http://msdn.microsoft.com/en-us/library/system.net.security.sslstream%28v=vs.110%29.aspx
Side Notes
Securing the transport of your data does not secure your app, do not make the mistake of thinking you get automatic security
If you choose to make your own server and client you can use either openssl to generate your certificate or you can use makecert which is part of .NET to make your certificate.

Just form a regular TCP connection between the applications, and write up a simple packet protocol (EG, 4 bytes indicate packet size, followed by packet data)
Except the data within this base-level packet is encrypted through System.Cryptography.AesManaged
If you have trouble encrypting the packets using AesManaged, try using The Encryptamajig - if that doesn't help, post further questions and we'll give you further specific help.
-- You can either have both sides know the password ahead of time (EG, tell the person at the other end the password in person), or quickly pass it unencrypted at the start of the connection (or, rather, encrypted with a default known password)
Not necessarily the best method but it should do the job.

Why not just the regular HTTPS? HTTP is just one level above TCP but it is far easier to work with and firewalls tend to be generally easy on HTTP/HTTPS ports namely 80 and 443. Of course, plain HTTP is not suitable for you but can you not use HTTPS instead of coming up with your own encrypted communication mechanism? In the client side (C#), all .NET classes such as HttpClient supports HTTPS very well. I quote Ayende in support of my suggestion to go with HTTP :)

Windows network authentication the right way

I am about to start on a project that will be running as a windows service listening for incoming connections and doing some things locally then sending a reply message. I understand the basic concepts with sockets and communicating over the network, however the things the service are doing could very easily abused. I would like to authenticate the person connecting, preferably against the windows local users on the machine the service is running, to see if they have windows administrative/power user rights.
I know how to do it check the rights once I have their information but I know sending the user name and password to the application over the network in the clear is a no no. I was thinking of just encrypting the password with some secret key but I know "trying to be clever" is the worst possible thing you can do in cryptography so I wanted to know what is the "correct" way to handle this situation.

My second idea was just create a shared self signed certificate between the client and the server and just use TLS for the entire connection.

I may as well post what I was thinking of doing, if it is the right thing to do say so in the comments.
Both the client and server will have a PSK at run-time the server will send a random number to the client. the client will encrypt the credentials with the PSK and the random number as the IV. It will send back the encrypted blob plus whatever commands it needs done.
I am not concerned about replay or mitm attacks. I just want to authenticate the user and not have peoples passwords blasted all over the network.

Scott,
this may be a bit overkill and a bit off topic, but have you considered using a web service interface to serve your clients (instead of using raw sockets)?
ASP .Net web service interfaces are easy to implement, and in the end, you'll end up with a very well defined interface. They also have support for authentication and secure communication.
ASP .Net Web Service Tutorial
HTTP Security and ASP.NET Web Services

Secure communication between a C# client and a PHP Server

I am maintaining a C# app that's been cracked by people creating spoof auth servers.
I want to encrypt all the communications between the client and server to prevent this happening to my next release.
I can see that PHP has a way to secure stuff.
http://www.php.net/manual/en/function.openssl-private-decrypt.php
What I can't find is the C# that will allow me to use the same built in libraries.
Can anyone help?

Did you look into SslStream?