I want to generate 512 bit RSA keypair and then encode my public key as a string. How can I achieve this?
For output as Hex-String
import java.security.*;
public class Test {
public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchProviderException {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(512);
byte[] publicKey = keyGen.genKeyPair().getPublic().getEncoded();
StringBuffer retString = new StringBuffer();
for (int i = 0; i < publicKey.length; ++i) {
retString.append(Integer.toHexString(0x0100 + (publicKey[i] & 0x00FF)).substring(1));
}
System.out.println(retString);
}
}
For output as byte values
import java.security.*;
public class Test {
public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchProviderException {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(512);
byte[] publicKey = keyGen.genKeyPair().getPublic().getEncoded();
StringBuffer retString = new StringBuffer();
retString.append("[");
for (int i = 0; i < publicKey.length; ++i) {
retString.append(publicKey[i]);
retString.append(", ");
}
retString = retString.delete(retString.length()-2,retString.length());
retString.append("]");
System.out.println(retString); //e.g. [48, 92, 48, .... , 0, 1]
}
}
Thank you very much! If i should get result like this [48, -137, -97, 49, 13, 6, 8, 42, -122, 72, -122, -9, 13, 2, 3, 15 4, 0, 3, -132, -115, 0, 48, -127] should i use just toString method instead retString.append(Integer.toHexString(0x0100 + (publicKey[i] & 0x00FF)).substring(1)); ??
If I want the output in PEM format then how do I do it?
to output as HEX the simpler solution is to use
javax.xml.bind.DatatypeConverter.printHexBinary(publicKey)
@YatinGrover for PEM Base 64 you can usejavax.xml.bind.DatatypeConverter.printBase64Binary(publicKey)
Also you can consider org.apache.commons.codec.binary.Hex#encodeHexString as a way to get a hex string from an array of bytes.