Decode and Inspect SSL Certificates Instantly SSL Certificate Decoder tool for network operations.

The tool works by first validating the input PEM certificate, checking if it starts with the required -----BEGIN CERTIFICATE----- header. If valid, it proceeds to remove this header and any whitespace characters from the input string, resulting in a base64-encoded string. This string is then decoded into a binary format using the atob function, which is part of the JavaScript Web API. The binary data is stored in a Uint8Array, allowing for easy manipulation and parsing.

The tool uses basic ASN.1 DER parsing to extract relevant information from the binary data. It searches for specific byte sequences that indicate the start of PrintableString, UTF8String, or IA5String sequences, which contain human-readable strings such as country names, organization names, and common names. These strings are then extracted and stored in an object for later use. The tool also uses a heuristic approach to extract fields like country, state, locality, organization, and common name from the parsed strings.

The extracted information includes details about the certificate itself, such as its total size and base64 length. Additionally, the tool attempts to detect the signature algorithm used in the certificate by searching for specific strings that match known algorithms like sha256WithRSAEncryption or ecdsa-with-SHA256. The results are then displayed in a user-friendly format, with each field labeled and formatted accordingly. The tool uses React hooks to manage its state and handle user input, allowing it to update the display dynamically as the user interacts with it.

The code relies on modern JavaScript features like ES6+ syntax and React hooks to manage state and side effects. It also utilizes browser APIs like the TextDecoder interface to decode binary data into human-readable strings. The use of client-side JavaScript and browser APIs ensures that no data is sent to servers, keeping the tool secure and private. The mobile-first responsive design allows developers to decode SSL certificates on-the-go, making it a convenient resource for anyone working with SSL certificates.