e203. creating a signature.txt

这里面包含了一百多个JAVA源文件

See also e198 Generating a Public/Private Key Pair and e202 Listing All Available Signature Algorithms. 
    // Returns the signature for the given buffer of bytes using the private key.
    public static byte[] createSignature(PrivateKey key, byte[] buffer) {
        try {
            Signature sig = Signature.getInstance(key.getAlgorithm());
            sig.initSign(key);
            sig.update(buffer, 0, buffer.length);
            return sig.sign();
        } catch (SignatureException e) {
        } catch (InvalidKeyException e) {
        } catch (NoSuchAlgorithmException e) {
        }
        return null;
    }