public JWTPolicyBean withSigningKeyString(String signingKeyString) {
        this.signingKeyString = signingKeyString;
        return this;
    }
Signing Key
<p>
To validate JWT. Must be Base-64 encoded.

@param signingKeyString
           The signingKeyString
@throws Exception key parsing exceptions
plugins/jwt-policy/src/main/java/io/apiman/plugins/jwt/beans/JWTPolicyBean.java