Is there a workaround for: java.lang.RuntimeException: Could not generate DH keypair [duplicate]

Question

I am testing a Java application. I am trying to start an SSL handshake using DH ciphersuite. but I am getting the following error:

java.lang.RuntimeException: Could not generate DH keypair

Some people have suggested BouncyCastle, but many people have reported errors with it, so I am not encouraged to use it if there is another alternative.

One have suggested downloading Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files from http://www.oracle.com/technetwork/java/javase/downloads/index.html. I did replaced the following two files java.security and java.policy in C:\Program Files (x86)\Java\jre7\lib\security. Note that I also noticed that I have Java\jre7\security installed in: Program Files (x86) and Program Files and I replaced both. But, I still see the same error.

Is there any workaround for this error ?

EDIT: The stack trace:

javax.net.ssl.SSLException: java.lang.RuntimeException: Could not generate DH keypair
    at sun.security.ssl.Alerts.getSSLException(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.handleException(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at MyClass.MyClass.myFunction(MyProg.java:78)
    at MyClass.MyClass.main(MyClass.java:233)
Caused by: java.lang.RuntimeException: Could not generate DH keypair
    at sun.security.ssl.DHCrypt.<init>(Unknown Source)
    at sun.security.ssl.ClientHandshaker.serverKeyExchange(Unknown Source)
    at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
    at sun.security.ssl.Handshaker.processLoop(Unknown Source)
    at sun.security.ssl.Handshaker.process_record(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
    ... 4 more
Caused by: java.security.InvalidAlgorithmParameterException: Prime size must be multiple of 64, and can only range from 512 to 1024 (inclusive)
    at com.sun.crypto.provider.DHKeyPairGenerator.initialize(DHKeyPairGenerator.java:120)
    at java.security.KeyPairGenerator$Delegate.initialize(Unknown Source)
    ... 11 more

EDIT2: My code is acting as a client trying to initiate SSL handshake with a remote server (website). I set the client's cipher suite list to:

{
"TLS_ECDHE_RSA_WITH_RC4_128_SHA",
"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA", 
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
"TLS_ECDHE_RSA_WITH_NULL_SHA",
"TLS_DHE_RSA_WITH_AES_128_CBC_SHA256",  
"TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
"SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA",
"SSL_DHE_RSA_WITH_DES_CBC_SHA",
"SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA"
};

All ciphersuites in the client's list are supported by Java. How can configure the Java client to support initiating an SSL handshake when the server offers long DH keys ?

Answer 1

Yes, basically dupe of #6851461 also #9162249 and #10687200. Unlimited strength policy is NOT the solution.

The prime size for DHE (and other DH) in SSL/TLS client is and must be set from the parameters received from the server, the client can't choose something different. (That's the ClientHandshaker.serverKeyExchange in the stacktrace.)

You already have ECDHE-RSA (which works okay in Java 7, or 6 if you add an ECC provider such as but not necessarily BouncyCastle) prioritized over DHE-RSA, and the server didn't choose it. You aren't offering plain-RSA; if you are willing to go without Forward Secrecy and the server is also, try adding at least some suites like _RSA_WITH_AES_128_CBC_SHA _RSA_WITH_RC4_128_SHA before (or instead of) the _DHE_RSA ones.

Another possibility is to ask the server operator(s) to use DH 1024-bit, if they're willing and permitted. It's not actually broken yet, but it is prohibited by some important standards.