protected void configureSigningKey(final String signingSecretKey) {
        try {
            if (ResourceUtils.doesResourceExist(signingSecretKey)) {
                configureSigningKeyFromPrivateKeyResource(signingSecretKey);
            }
        } finally {
            if (this.signingKey == null) {
                setSigningKey(new AesKey(signingSecretKey.getBytes(StandardCharsets.UTF_8)));
                LOGGER.trace("Created signing key instance [{}] based on provided secret key", this.signingKey.getClass().getSimpleName());
            }
        }
    }
Sets signing key. If the key provided is resolved as a private key,
then will create use the private key as is, and will sign values
using RSA. Otherwise, AES is used.

@param signingSecretKey the signing secret key
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/cipher/AbstractCipherExecutor.java