Creating an RSA Public Key from a String

Question

I created this test public key using 1024 RSA, and then encoded it on DER and Base64 on a different coding platform. I copied the key to a string in Android / Eclipse and I'm trying to turn it into a public key using KeyFactory. It just keeps giving me an InvalidKeySpecException no matter what I try. Any advice at all would be appreciated.

     private void prepKeys() {
         String AppKeyPub = "MIGHAoGBAOX+TFdFVIKYyCVxWlnbGYbmgkkmHmEv2qStZzAFt6NVqKPLK989Ow0RcqcDTZaZBfO5" +
"5JSVHNIKoqULELruACfqtGoATfgwBp4Owfww8M891gKNSlI/M0yzDQHns5CKwPE01jD6qGZ8/2IZ" +
"OjLJNH6qC9At8iMCbPe9GeXIPFWRAgER";

        // create the key factory          
            try {
                KeyFactory kFactory = KeyFactory.getInstance("RSA");  
                // decode base64 of your key
                byte yourKey[] =  Base64.decode(AppKeyPub,0);
                // generate the public key
                X509EncodedKeySpec spec =  new X509EncodedKeySpec(yourKey);
                PublicKey publicKey = (PublicKey) kFactory.generatePublic(spec);

            System.out.println("Public Key: " + publicKey);  

            } catch (Exception e) {
                // TODO Auto-generated catch block  
                e.printStackTrace(); 
            }

         }

Answer 1

PKCS # 1 SubjectPublicKeyInfo, Java. PKCS # 1 - RSA, , . SubjectPublicKeyInfo PKCS # 1 - RSA.

PKCS # 1 SubjectPublicKeyInfo, , RSA SubjectPublicKeyInfo. , Bouncy Castle. , .

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BER- BigInteger. , BER/DER .

Bouncy Castle ( API) :

String publicKeyB64 = "MIGHAoGBAOX+TFdFVIKYyCVxWlnbGYbmgkkmHmEv2qStZzAFt6NVqKPLK989Ow0RcqcDTZaZBfO5"
        + "5JSVHNIKoqULELruACfqtGoATfgwBp4Owfww8M891gKNSlI/M0yzDQHns5CKwPE01jD6qGZ8/2IZ"
        + "OjLJNH6qC9At8iMCbPe9GeXIPFWRAgER";
// ok, you may need to use the Base64 decoder of bouncy or Android instead
byte[] decoded = Base64.getDecoder().decode(publicKeyB64);
org.bouncycastle.asn1.pkcs.RSAPublicKey pkcs1PublicKey = org.bouncycastle.asn1.pkcs.RSAPublicKey.getInstance(decoded);
BigInteger modulus = pkcs1PublicKey.getModulus();
BigInteger publicExponent = pkcs1PublicKey.getPublicExponent();
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, publicExponent);
KeyFactory kf = KeyFactory.getInstance("RSA");
PublicKey generatedPublic = kf.generatePublic(keySpec);
System.out.printf("Modulus: %X%n", modulus);
System.out.printf("Public exponent: %d ... 17? Why?%n", publicExponent); // 17? OK.
System.out.printf("See, Java class result: %s, is RSAPublicKey: %b%n", generatedPublic.getClass().getName(), generatedPublic instanceof RSAPublicKey);

, , , , ASN.1/BER Bouncy Castle.

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, Base 64 Android (android.util.Base64). Java.

Answer 2

, Bouncy Castle

public class RSAKeySeperation {


public static void main(String[] args) throws InvalidKeySpecException, NoSuchAlgorithmException {
    String publicKeyB64 = "MIIBITANBgkqhkiG9w0BAQEFAAOCAQ4AMIIBCQKCAQBV8xakN/wOsB6qHpyMigk/5PrSxxd6tKTJsyMIq5f9npzZue0mI4H2o8toYImtRk6VHhcldo0t7UwsQXmFMk7D"
            + "i3C53Xwfk7yEFSkXGpdtp/7fbqNnjVoJl/EPcgoDsTPrHYF/HgtmbhzuYvYeY1zpV0d2uYpFxAuqkE9FreuuH0iI8xODFe5NzRevXH116elwdCGINeAecHKgiWe"
            + "bGpRPml0lagrfi0qoQvNScmi/WIN2nFcI3sQFCq3HNYDBKDhO0AEKPB2FjvoEheJJwTs5URCYsJglYyxEUon3w6KuhVa+hzYJUAgNTCsrAhQCUlX4+5LOGlwI5gonm1DYvJJZAgMBAAEB";
    byte[] decoded = Base64.getDecoder().decode(publicKeyB64);
    X509EncodedKeySpec spec =
            new X509EncodedKeySpec(decoded);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    RSAPublicKey generatePublic = (RSAPublicKey) kf.generatePublic(spec);
    BigInteger modulus = generatePublic.getModulus();
    System.out.println(modulus);
    BigInteger exponent = generatePublic.getPublicExponent();
    System.out.println(exponent);
}

}