Get a fingerprint (String SHA-256) from a android.content.pm.Signature Object

androidcertificate_fingerprint.java

/**
 * Get fingerprint from a certificate in android.content.pm.Signature
 * @return String fingerprint that contains the SHA-256 digest
 */
private static String getFingerprint(android.content.pm.Signature ce){
    String certificate = "";
    InputStream input = new ByteArrayInputStream(ce.toByteArray());

    CertificateFactory cf = null;
    try {
        cf = CertificateFactory.getInstance("X509");


    } catch (CertificateException e) {
        e.printStackTrace();
    }
    X509Certificate c = null;
    try {
        if (cf != null) {
            c = (X509Certificate) cf.generateCertificate(input);
        }
    } catch (CertificateException e) {
        e.printStackTrace();
    }


    try {
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        byte[] publicKey = new byte[0];
        if (c != null) {
            publicKey = md.digest(c.getEncoded());
        }


        StringBuilder hexString = new StringBuilder();
        for (byte aPublicKeybyte : publicKey) {
            String appendString = Integer.toHexString(0xFF & aPublicKeybyte);
            if (appendString.length() == 1) hexString.append("0");
            hexString.append(appendString);
        }

        certificate = hexString.toString();
    } catch (NoSuchAlgorithmException | CertificateEncodingException e1) {
        e1.printStackTrace();
    }
    return certificate;
}