A Guide to Decoding Keys 10 -12 of Cardano x509 Certificate Metadata

x509 Certificate metadata and related metadata are within a x509 Registration/Update transaction.

The Structure of an x509 certificate metadata contains 5 keys:

• 0:Purpose - 128bit UUID V4 of the metadata purpose
• 1:txn-inputs_hash - Hash of the transaction inputs
• 2:previous_transacton_id - Hash of the immediate proceeding transaction in a series of updates.

10,11,12: 509 chunked data - Compressed x509 update data

• 99:Validation signature - Signature over the entire auxiliary data attached to the transaction.

Key 10, 11 or 12 - x509 chunked data.

It used to store large x509 RBAC (Role-Based Access Control) registration data in Cardano transaction metadata.

Core Requirements

• A Role 0 signing key must always be defined. -I t must be tied to an on-chain key (e.g., a stake address hash).
• The RBAC data references the transaction it’s attached to and can’t be validated independently.

Encoding & Compression Process

• Prepare x509 Role Registration Data and encode with dCBOR → raw data.
• Compress the raw data using: Brotli, or ZSTD, or No compression (raw) if smaller.
• Choose the smallest result (Raw, Brotli, or ZSTD). Split the chosen data into 64-byte chunks (last chunk may be shorter). Store chunks in an array under one of these metadata keys:
• • 10 → Raw (no compression)
  • 11 → Brotli compressed
  • 12 → ZSTD compressed

Step by Step Process of Decoding Keys 10 -12 of x509 Certificate Metadata

1. This is the main invoke method in the action class.

1. Rebuild the certificate bytes.

1. Extract certificate from CBOR

1. Extract Ed25519 public key:

1. Generate Catalyst Profile ID

1. Extract Stake Address