ASN.1 Viewer

A targeted tool to decode and visualize ASN.1 structures from hex or base64 inputs, aiding developers, security analysts, and educators.

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About This Tool

The ASN.1 Viewer decodes ASN.1 encodings to reveal their hierarchical TLV structure and relationships. It accepts data as hex, base64, or PEM blocks and outputs a tree-like representation suitable for protocol debugging and PKI analysis. The tool emphasizes correctness and reproducibility by providing both a human-readable description and a machine-readable JSON mapping of nodes. It supports DER, BER, and CER encodings, producing a tree that mirrors the encoding layout and shows parent-child relationships. This enables quick verification of encoding rules, tag types, and lengths. The distinguishing value is a deterministic, exportable representation that can be consumed by other tools or automated tests, reducing manual parsing effort and potential errors. Typical use cases include certificate inspection, TLS handshake message analysis, PKI workflow validation, and classroom demonstrations of ASN.1 concepts. The tool is designed to be lightweight, dependency-free, and suitable for integration into security tooling or standalone analysis via API.

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How to Use

Provide inputs: data_input with hex, base64, or PEM; specify input_format.
Optional: enable PEM handling if feeding PEM blocks.
Run decoding: the tool parses the TLV structure and generates a JSON tree.
Review outputs: examine root tag, total node count, and any reported errors.
Export results: download JSON or copy to clipboard for integration.

Frequently Asked Questions

Find Quick Answers

What inputs are supported?

The tool accepts hex strings, base64 strings, or PEM blocks containing ASN.1 data. It can auto-detect DER/BER encoding and construct the corresponding TLV tree.

What outputs are produced?

Primary output is a tree_json object representing the TLV hierarchy with fields such as tag, length, value, and children. Additional outputs include a root_tag summary and an errors array if present.

Is this a full ASN.1 schema validator?

No. It provides a structural decoding and visualization of ASN.1 encodings, not full schema validation or cryptographic verification.

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