We have generated RSA public key by our java program to encrypt the data in C++ before transmitting it but when we use this key to encrypt the data using Microsoft encryption API, it doesn't accepts this key.
Do anyone has any ideas on this?
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Perhaps the M$ API requires a binary key, and the key you're giving it is a base64-encoded key block. Or vise-versa. What's the error message it's giving?amphetamachine– amphetamachine2010-01-27 07:19:09 +00:00Commented Jan 27, 2010 at 7:19
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Your best chance to get help would be to show us a complete example - including data - of the code that fails to accept the key.Rasmus Faber– Rasmus Faber2010-01-27 19:14:12 +00:00Commented Jan 27, 2010 at 19:14
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2 Answers
Microsoft code has some intrinsic limitations on what RSA keys it can use: it requires the public key length (the modulus bit length) to be a multiple of 16, and the public exponent must fit in a 32-bit unsigned integer.
However, most RSA keys fit in those constraints and the usual suspects are encoding/decoding issues. Java tends to use big-endian everywhere, because:
- that's what is mandated by ASN.1-based encoding rules;
- Java is from Sun who hast long dealt with big-endian hardware (68020, Sparc).
On the other hand, Microsoft's CryptoAPI wants little-endian. You may have used your public modulus in the wrong order.
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In my experience the serialization of an RSA key is different between Java and MS.
But, what I did was to use the Bouncy Castle API to do this, as they have a Java and .NET version of their library.
For more options you can look at this question: RSA: How to generate private key in java and use it in C#?
