Tools for ASN.1 are available on almost all operating systems. They generate code for popular . ASN1 Viewer (Objective Systems, Inc.) Free Java BER/DER. Click the "Browse" button and navigate to the file you want to analyse. The ASN1 decoder is useful for certificates, stored keys, and many types of TLV encoded. Online decoder for ASN.1 encoded HEX or PEM. This is a tool I used when working with X certificates.