Abstract Syntax Notation.1 (ASN.1) is a data format for representing, encoding, transmitting and decoding data. It provides a set of formal formats for describing the structure of objects, regardless of how the language is executed and the specific designation of these data, regardless of the application. Common CA certificates, PEM, CER, PFX, etc. all use ASN.1 encoding. For easy reading, this tool will display the decoding result in xml format. Since the understanding of ASN.1 is not deep, deviations may occur in some data processing. When you find an error, please correct me.