A friend and me are working on a Java Game with a client/server - architecture.
It is working well, but i ran into a problem.
We use TCP Sockets for networking between server and client.
Our network protocol isnt encrypted and can just be read by anone who bothers to watch the stream.
We thought about how we could apply some kind of cryptography to it to hide login information and prevent people to write their own clients. But basic things like adding/substracting bytes seems pretty easy to figure out.
What are the usual methods used to encrypt network communication for games( or at least game login information )? And having written the server and client in java, are there any useful java libraries?
Use public-key encryption (RSA for example) and implement something like the SSL Handshake, or of course use SSL - here you can see an example.
Here's a simplified sequence:
the server sends his public RSA key to the client
the client generates a symmetric key (using AES for example)
the client encrypts the symmetric key with the server's public key and sends it to the server
the server decrypts the received symmetric key
Now both the client and the server have a key which no one eavesdropping can know. Then use that key to encrypt all data.
SSL(Secure Sockets Layer) is popular to handle this kind of problem.
Look at the javax.crypto library or bouncyCastle.
Both provide cryptographic primitives, also for encryption. Depending on how secure you want to have it, you can use symmetric or assymetric crypto. However, also think about key management in advance. Where do you store your private/shared key.
If it is a client-server, the best way would be to use assymetric crypto (i.e. RSA, Elliptic Curve) and give every user a certificate signed with the key of the server (note, this is TLS (formerly called SSL)). This way you can check if the user logging on is authentic. However, you dont prevent custom clients since the user has to have everyone can just copy the certificate.
In practice, it is quite hard to prevent custom clients.
You can use Ciphers. Some more examples here and here
Related
I'm writing a CMP server and I have a problem.
It is used in a centralized PKI where the RA send a private key with the associated certificate to the server, that we have to relay to the CMP client.
The problem is that I can't find how we are supposed to encrypt the private key to send it to the client and for him to be able to decrypt it.
Do we only rely on the security of https, because it sounds wrong ?
Did I miss something in the CRMF RFC ?
A solution would be, I guess, to generate a temporary keypair from the client and use it for encryption/decryption but is sounds more like a hack than the way to do it properly.
It is easy to do when the client is the one generating his keypair, but in this specific case, everything is generated by our OpenTrust RA.
PKCS#12 can be used to distribute private keys from an RA to the various clients. We have used a hardware USB token for this purpose. Data on the USB token can only be decrypted by the software on the client side (using a pre-shared secret).
If you don't want to use hardware tokens, the only option you have is to use a pre-shared secret (communicated via some out of band/out of channel means) and use that symmetric key to distribute the private key and transmit it over HTTPS. Also make sure your HTTPS is configured to use at least AES-256.
I am developing an Android app. The app communicates with a server through a PHP API. Each user must create an account. So, the app has a login functionality. I am doing further research on how to be able to securely transfer data between client (Android app) and server. For example, a user sends, through a POST, request his username/password in order to login.
Based on what I have read, I can safely assume that in case someone “listens” the transaction between client and server he could steal the username/password combination and use it on order to login to the legitimate user’s account. Is that correct?
The solution to this problem is to encrypt the data (eg username and password) before sending them either from client or server. The data will be then decrypted by the recipient (client or server). I do that by using crypt/decrypt functions both on client (written in Java) and server (written in PHP). Each function has the same IV (initialization vector) and Secret Key (to be honest, I do not know much about the IV’s usage so forgive me if I say something wrong. I google around for information but any useful links would be really appreciated).
From what I read, the problem with this implementation is that the APK file could be decompiled from client side and get the IV and Secret Key. As a result, a listener could decrypt the data sent. Is that correct?
Trying to find a solution to this problem I have a suggestion and I would like your opinion. What if during user’s registration a unique IV and secret key are given to the each user. These values are stored both to a MySQL database (server side) and a SQLite database (client side). Whenever data needs to be sent trough a post request, the user’s id (could be something simple as an integer) and the data to be sent are encrypted using the unique IV/Secret Key for the individual user. These are stored locally so the “listener” has no access to them. Even if he decompile the APK he will just have access to his own IV/Secret Key that he already knows. Then on server side the data are decrypted using the same IV/Secret Key stored on the server. The same procedure is applied when data are sent from server to client.
Is this a correct approach?
Reusing the same symmetric key and same IV is extremely incorrect approach and must not be used ever.
Reusing the same key and IV will enable attacks where the attacker will be able to recover your secret key just be eavesdropping on the encrypted traffic for long enough. And when the attacker has your key he will be able to decrypt all and every past and future communications.
To secure the data transfer you should use HTTPS (or SSL/TLS directly if your data transfer protocol is not HTTP-based).
If your only concern is to securely communicate with the server i suggest you to install a ssl certificate to your server. Doing this way the communication will be secured by the underlying protocol. To facilitate your communication with the server for implementing ssl communication i suggest you to use aquery library, here's a link!.
Also dont forget to see the ca compatibility list for android.
Hope it helps.
This is a rather old question so i'm surprised it didn't have a more complete response. It seems you understand the concepts of symmetric encryption but you are missing knowledge of public/private key encryption. Look up RSA for a method of achieving public/private key encryption. With this, you can generate (via the assistance of a cryptographically secure RNG) new random keys as well as IVs at the start of each session to feed to your symmetric encryption system. This means that anyone listening from start to finish will not be able to make sense of your system short of brute forcing the RSA key or the symetric(AES?) key.
I am building my website in which I am facing problems with implementing encryption. I am developing it using RESTful web services in java.
I found GibberishAES API for encryption from javascript. The encrypted message now goes to web service, but I have no clue how to decrypt it in the (java) web service. I know GibberishAES is not available in java, but is there any roundabout way?
Or, are there any encryption APIs which are supported for both Java and Javascript?
I also have the issue with (symmetric) key distribution for the website. It will have 100's of client (machines, in public network) and I don't know how to communicate the unique key for a particular machine to it.
Please help me with pointers in this regard.
GibberishAES implements AES encryption. AES is a symmetric cipher, that means that both parties must know a shared key. The problem of distributing the key is not trivial, and there exist well-known algorithms for doing so.
As it was mentioned in some comments, SSL already solves that problem, because it negotiates the generation of a distributed secret key, that is later used for encryption. If for any reason you cannot use SSL, you should adopt some mechanism for secure generation or transport of the secret key. For instance, you could generate a ephimeral RSA key pair in the client, send the public key to the server, and have the server return the secret (AES) key in wrapped form.
I need to make two java proceses on the same host to communicate securely. I do not need to authenticate the processes so I don't want to use certificates.
I want to generate a random key in the server and client, exchange the keys between the processes using Elgamal; establish common symmetric key across the processes; and then communicate securely.
As far as I can think of, this can be done by implementing RMIServerSocketFactory and RMIClientSocketFactory interfaces to establish symmetric key as discussed above.
Is there already an implementation to do that?
Or is there a way to configure SslRMIServerSocketFactory and SslRMIClientSocketFactory to start using ElGamal as the key exchange protocol
ElGamal is preferred choice over RSA as ElGamal will generate random symmetric keys for each handshake while RSA will generate static keys every time.
I need to make two java proceses on the same host to communicate
securely. I do not need to authenticate the processes so I don't want
to use certificates.
Your reasoning is flawed from the start unfortunately. However "hardened" a communication channel is, you'll always want to make sure you're communicating with the intended party if you want to exchange data secretly. Authentication in one form or another is necessary to do so.
In theory, you can do away with certificates and use PSK cipher suites (which would effectively include the authentication step). This isn't supported by default with the Oracle/OpenJDK JRE. In addition, if you're working on the assumption that your certificate's private key would be compromised (as suggested by your other question), the same problem could happen with the pre-shared keys anyway.
I am trying to make a PHP script to interact a with a Java application. They will share some information, so I would like to encrypt the data that is passed between them to make it as secure as possible, on top of having an SSL certificate. However, because my website is only on a shared server at JustHost, as far as I am aware I can not use the 'mcrypt' PHP module, so I'm not sure how to do it so that both my Java application and the PHP script can encrypt data being sent and decrypt data being received!
Your SSL conversation between Java and PHP will protect it your data while it's in transit. Should you properly protect the private key with a strong password (10+ symbols) and make sure your algorithms strong no one will be able to break it by snooping on the conversation.
You won't get any extra protection by encrypting the data before sending it over the SSL conversation. And you actually might be weakening your security because in order for you to encrypt data you'll have to share some key should you choose symmetric encryption. And, by trading secret keys you're undoing much of the protection SSL gives you because the huge benefit of SSL is the fact we can encrypt data without agreeing on a secret key. If I were trying to get at your encrypted text I'd attack your client because it's easier to find your symmetric encryption key than it is to break SSL. And while you could use asymmetric encryption you'll be basically re-inventing SSL.
I would focus on making sure your SSL conversation is strong. Using only the strongest symmetric encryption: TripleDES, IDEA, AES if your server supports it. Take out the weaker algorithms so conversations can't use the weaker encryption. Generate 1024+ public/private key pairs. That might not always be easy on your shared server, but your Java application could only choose to use TripleDES, IDEA, and AES.
Make sure you validate the server's certificate on the client side so you ensure you aren't talking to a false service. That basically means taking the server's certificate and adding it to the keystore used on the client. If that's Java you can use keytool to import a certificate and use that keystore as your TrustManager/KeyManager in your SSL conversation.
If you want to encrypt the data after it's gone over the SSL conversation then you can encrypt/decrypt on the server only. But, you still have a key management problem. If you encrypt/decrypt how do you plan on securing the secret key on the server? That's always the ugly problem that doesn't have a simple answer.