how to construct a java.security.interfaces.RSAPublicKey?

Tags: , , ,



I have the following string, which I understand to be an RSA public key:

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAi+VPTFioJ3Dv/D6aEMqkiESiRkKBnISe3+K7vJDMAMqkTCfGz0jKInS5BXQUW9jRqkgBpSKdwizIWhCBOT3wGmgnm+L3bVwtTML52drqePSmQgfHAiWfcLdZuFGULtpy5nhaOAR5nzuDmDR8L0vumNbhqK+o9jbwSTbm8cfUsf7xHc7RX+bJinu5s566NtxqJ0y8U764BVPg96QLKpOEiNJUELarkdnljjdb12Gvs+631YFKAnUt5V9oHowBS1JDerlbhHKH6kYKEuVZfm5ofvhGQiUU69i9q/hO5Pb0eIZsogazERJmEIIvre8sQLNE71ti0WD3i7QDGlnsoai6EwIDAQAB

I need to construct a java.security.interfaces.RSAPublicKey from this string. First I tried calling RSAPublicKeyImpl.newKey(myString.getBytes(StandardCharsets.UTF_8)), but that threw the following exception:

java.security.InvalidKeyException: invalid key format
"sun.security.x509.X509Key.decode(X509Key.java:387)"
"sun.security.x509.X509Key.decode(X509Key.java:402)"
"sun.security.rsa.RSAPublicKeyImpl.<init>(RSAPublicKeyImpl.java:122)"
"sun.security.rsa.RSAPublicKeyImpl.newKey(RSAPublicKeyImpl.java:72)"
"com.myApp.getPublicKeyRsa(KeyLoader.java:33)"

Then, following an online guide, I tried this code instead:

KeyFactory keyFactory = KeyFactory.getInstance("RSA");
X509EncodedKeySpec pubSpec = new X509EncodedKeySpec(myString.getBytes(StandardCharsets.UTF_8));
keyFactory.generatePublic(pubSpec);

That threw a very similar exception, just wrapped in another one.

Am I missing something obvious here? How do I construct a RSAPublicKey?

Answer

this method can help you

  public static PublicKey stringToPublicKey(String publicKeyString)
        throws NoSuchAlgorithmException,
        NoSuchPaddingException,
        InvalidKeyException,
        IllegalBlockSizeException,
        BadPaddingException {

    try {
        if (publicKeyString.contains("-----BEGIN PUBLIC KEY-----") || publicKeyString.contains("-----END PUBLIC KEY-----"))
            publicKeyString = publicKeyString.replace("-----BEGIN PUBLIC KEY-----", "").replace("-----END PUBLIC KEY-----", "");
        byte[] keyBytes = Base64.decode(publicKeyString, Base64.DEFAULT);
        X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");

        return keyFactory.generatePublic(spec);

    } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
        e.printStackTrace();

        return null;
    }
}


Source: stackoverflow