Key from a String

Question

Hi to all,
i have a big problem.
I must set an RSA key value (Modulus and Exponent) from a String conteining the encrypted value
( for example :hVqLzLgUeZTxQ95UdJDTpIwbf6F7v.... ).
Is possible to do this ?
I didn't found classes and method to do this from the API.
Somebody can help me?
thank you!

Answer 1

ghstark wrote:
z4c4gn0 wrote:
Hi to all,
i have a big problem.
I must set an RSA key value (Modulus and Exponent) from a String conteining the encrypted value
( for example :hVqLzLgUeZTxQ95UdJDTpIwbf6F7v.... ). Is possible to do this ?
I didn't found classes and method to do this from the API.
Somebody can help me?
I cannot offer much help without more clarifying details, though perhaps others can deduce what you need. Just from the little you have written, I might guess that you have a base64 encoded (*not* encrypted) string or strings containing the RSA modulus and exponent. In that case, I know sabre150 has shown what to do, so search this forum for posts containing keywords "XML " and "RSA". Also, examine the class http://java.sun.com/javase/6/docs/api/java/security/spec/RSAPublicKeySpec.html as well as the base64 decoders from the jakarta commons codex classes.
I must get the keyinfo from an XML Signed file, and use this parameters for sign another one, so
i have my class that return the String value of RSA Module and Exponent parsed.
Now i need to sign using this parameters, and i tried the RSAPublicKeySpec that you said
in this way:
String mod="blablalba"; //the string module parsed
String exp ="blablalba"; //the string exponend parsed
byte [] modbyte=mod.getBytes();
byte [] expbyte=exp.getBytes();
BigInteger modulus = new BigInteger(modbyte);
BigInteger publicExponent =new BigInteger(expbyte);
System.out.println(exp+" = "+publicExponent);
System.exit(0);
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, publicExponent);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
RSAPublicKey pk = (RSAPublicKey)keyFactory.generatePublic(keySpec);
that's work but don't return the right value of parameters, because Transform the strings in BigInteger.
What can i do?
thanks