I am creating a TCP connect with Flash to a C# daemon.
Now I have come to the part of encryption... I know that Flash is decompilable and so not safe to store private keys on.
I need 2 way encryption because of the messages that have to be send back to the Flash client.
I have been thinking and googling, but cannot find a proper solution yet.
Anybody got an idea??
You'd usually use a hybrid encryption.
Client opens a session on the server, acquiring public key for an asymmetric encryption.
Client generates a key for a symmetric encryption, and sends this key to the server, encrypted with the public key previously acquired.
The rest of the communication is encrypted using a symmetric encryption with they key now known to both client and server.
greetz
back2dos
back2dos' solution will work (and be the easiest) if your connection is SSL/TLS.
If you are forced to use regular sockets (e.g., the server does not have an SSL certificate), then you'll need to do the same by hand. In this case, you'll need to use a Diffie-Hellman key exchange, which enables the creation of a shared secret that is not actually sent over the wire.
Again, if possible, use back2dos' solution. It's a lot easier.
Related
How to use .NET 4.8 System.Net.Security.SslStream with external device (HSM) that keeps private RSA keys secure, as SslStream.AuthenticateAsServer requires X509Certificate with both public/private keys. How can I associate X509Certificate private key with HSM and pass SslStream validation to the remote secure device?
Is it even possible with microsoft ssl abstraction or should I rely on some custom ssl implementation (open-source library)?
I don't really know you architecture so I'm having issues give a good answer. He are some pointers
1) Whenever you encrypt something you always need to decrypt (or verify). So you always have two copies of the private key. One where it is used to encrypt and the other where it is used to decrypt (or verify)
2) When a key is on a file system you can always protect the file using credentials. But you cannot prevent somebody from remove the hard drive and reading on another system. So a HSM give physical protection of the drive so somebody cannot read your private key on by removing the drive.
3) You system has a red/black boundary where the red area is where data is not encrypted and black is where the data is encrypted. You would have a firewall which is the division between red and black areas. In you case you have three security areas where the third is a violet area (the HSM device) where the private key is protected.
The issue you are having is setting up the red/black/violet boundaries of your system. You have red data that needs to be encrypted with a certificate that is on the HSM. What I think you have is an internal red network (or database) with data that needs to be encrypted with the certificate before being sent out as encrypted black data. So I'm recommending to have a service on the HSM that does the encryption. So your red network to get data encrypted you would send to the encryption service. Then after being encrypted the data could the be sent out the firewall as black data.
I'm tasked with encryption of the network communication of our program and I've been thrown a wrench. I was going to use SslStream but my CTO would like to stay away from managing certificates. So I was wondering is there any other Stream that will encrypt data, or a way to dynamically generate certificates?
You could encrypt your data using a standard encryption algoithm (RSA, AES, PGP, etc.) as long as you control both endpoints. If not, you will need to use something like certificates since clients won't be able to otherwise decrypt. I'm not sure why your CTO would avoid certs, but nonetheless...
See this article for a good start: http://msdn.microsoft.com/en-us/library/0ss79b2x.aspx
Also note that WCF supports MANY means of communication encryption, many of which do not require certs.
WCF netTCPBinding - Is transport encryption enough?
Note finally that you cannot encrypt the message headers if you don't talk directly to the other party (ie: if there's anyone in the middle), since the middle part won't be able to decipher/route your message.
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 :)
I need to send data between SilverLight applications. I've got requirement that says that data should be transmitted using secure protocol such as SSL/TLS. Data is sent using TCP sockets due to performance reasons. Unfortunately SilverLight doesn't support SslStream. If I want to transmit data over SSL/TLS I need to buy third party library e.g. SecureBlackbox. I don't want to be dependent on third party libraries when it comes to handling transport layer.
However, SilverLight has CryptoStream class. I'm thinking of exchanging the key for symmetric encryption using WCF over SSL (SilverLight supports that) and then encrypt the data with AES using CryptoStream.
Is this solution safe? Can it be compared to using SSL/TLS in terms of security? Is there some obvious security hole that I'm missing?
I guess the main problems with the AES approach is key management and key verification. I'm sure you know that SSL uses a 'handshake', which uses a CA chain (Certificate Authority) to verify the validity of the SSL certificate. This all happens before an AES key is generated for the SSL session. So, by not using SSL, you miss this important step.
This means that you take on the responsibility for verifying that the keys are secure and exchanged in a secure manner.
I am using NServiceBus with MSMQ between my web application and service and I need to be able to encrypt the message payload so that if a message gets queued locally on the web server (service host is down) that sensitive data can't be viewed.
Because the web server is public facing, I am not only required to encrypt data that may be serialized to disk in anyway, but I also cannot store the encryption key on the web server.
I've considered using DPAPI to store the key, but since the key would be stored on the host I don't know yet if that runs afoul of the requirement or not. The other option I have considered is that when the web application starts it could request the key from a service and hold it in memory for the life of the application pool.
I haven't had to work with this level of requirement on encryption before and would like to find out what others are doing and get some feedback on the ideas mentioned above.
Can you use public/private key encryption? Then you only need to public key on the server, and the data is decrypted using the private key elsewhere.
"Because the web server is public facing, I am not only required to encrypt data that may be serialized to disk in anyway, but I also cannot store the encryption key on the web server."
Seems like this is the only constraint to focus on - validate that it is true for starters. It'll rule out DPAPI + local key-store approaches.
It's plausible to deliver the key by service, but that service still has to authenticate the caller. If your server is compromised masquerading as a legitimate caller, observing the call etc. are all possible. In addition if you stored the key only in-memory, that memory is still discoverable in a debugger or memory dump, elevated privilage process etc.
Hardware encryption cards are the only way to overcome the latter scenarios.
You can override the source from which NServiceBus pulls its encryption key - this is described in the docs here: http://docs.particular.net/nservicebus/security/encryption
This way, you can avoid having this sensitive information reside out on the DMZ.
The best place to encrypt is at the queue level. You do this by sending private messages and creating queues that only accept private messages. While you can set the queue privacy level when you create the queue at creation time, I'm not sure if you can configure NServiceBus to send private messages.