ASN.1 DER Structure Inspector

How to use ASN.1 DER Structure Inspector

Inspect one DER value as a bounded tag, length and value tree with exact offsets and selected primitive checks. Read DER bytes, hexadecimal text or one matching-label PEM block. Decode integers, object identifiers, selected strings and bit counts while preserving a short hex preview for uninterpreted content.

1. Provide optional local der or pem file, der hexadecimal or one pem block.
2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
3. Copy the result or download a separate output; reset to clear the current form.

Good to know

• One complete value, at most 1 MiB, 24 nesting levels, 1,000 values and tag numbers through 2^31−1. Indefinite, truncated and non-minimal lengths are refused before descending into content.
• Primitive checks cover Boolean, integer/enumerated sign octets, bit-string padding, OID components and selected string alphabets. Integer decimal previews stop at 32 bytes; long values retain a short hex preview.
• This is a structure inspector, not complete DER/schema validation. SET ordering, default omission, all character-string/time/REAL semantics and application-defined tags need their actual schema. No key or certificate is imported, executed or trusted.
• The PEM profile accepts one matching uppercase label and ASCII whitespace in the body. Multi-block bundles, surrounding prose and legacy encrypted-PEM headers are refused.
• Inputs are processed on this device and are not automatically saved or uploaded.