BIP122 Namespace - Interoperable Address

Namespace Reference

ChainType binary key: 0x0001

CAIP-104 namespace: bip122

Chain reference

See this namespace’s CAIP-2 profile. The chain reference is the first 32 characters (16 bytes) of the genesis block hash in lowercase hex.

Text representation

<genesis_hash_prefix>

This is the first 32 lowercase hex characters (16 bytes) of the genesis block hash as defined in BIP122.

Note: Per CAIP-350, the full chain identifier is bip122:<genesis_hash_prefix> (e.g., bip122:000000000019d6689c085ae165831e93, bip122:000000000933ea01ad0ee984209779ba).

Text representation -> customary (CAIP-2) conversion

The text representation (chain reference) is the same as the chain reference in the CAIP-2 chain identifier; no conversion is needed.

Customary (CAIP-2) conversion - text representation conversion

The chain reference in the CAIP-2 chain identifier is the same as the text representation; no conversion is needed.

Binary representation

The chain reference is the 16 bytes corresponding to the first 32 hex characters of the genesis block hash. Bytes are in the same order as the hex string (first two hex characters encode the first byte, etc.).

Text -> binary conversion

Decode the 32-character lowercase hex string to 16 bytes (RFC-4616 base16, no 0x-prefix).

Binary -> text conversion

Encode the 16 bytes as 32 lowercase hex characters (RFC-4616 base16, no 0x-prefix).

Examples

Addresses

See this namespace’s CAIP-10 profile. BIP122 supports multiple address types (P2SH, SegWit, Taproot) with different native encodings (base58btc, bech32, bech32m).

Text representation

<address>

Where <address> is the full native ASCII form (base58btc, bech32, or bech32m) as in CAIP-10—e.g. P2SH 35PBEaofpUeH8VnnNSorM1QZsadrZoQp4N, SegWit bc1qwz2lhc40s8ty3l5jg3plpve3y3l82x9l42q7fk, or Taproot bc1pmzfrwwndsqmk5yh69yjr5lfgfg4ev8c0tsc06e.

Text representation -> native representation conversion

No transformation; the text representation is the native representation.

Native representation -> text representation conversion

No transformation; the native representation is the text representation.

Binary representation

The binary representation uses a one-byte type prefix followed by the decoded payload (without checksum):

• 0x01 — P2SH: 1 byte version (network-dependent) + 20 bytes script hash (21 bytes total after type).
• 0x02 — Witness (SegWit / Taproot): 1 byte witness version (0 for P2WPKH, 1 for P2TR, etc.) + 20 or 32 bytes program (22 or 34 bytes total after type).

Checksums are omitted in binary; they can be recomputed when converting back to text.

Text -> binary conversion

1. Detect address type from prefix (e.g. 3 for P2SH, bc1q/tb1q etc. for witness).
2. Decode using the appropriate scheme (base58btc for P2SH, bech32/bech32m for witness) and strip checksum.
3. Prepend type byte 0x01 (P2SH) or 0x02 (witness), then append version byte and hash/program bytes as above.

Binary -> text conversion

1. Read the type byte (0x01 or 0x02).
2. For 0x01: read 21 bytes (1 version + 20 hash), encode with base58btc including checksum for the target network.
3. For 0x02: read 1 byte witness version, then 20 or 32 bytes program; encode with bech32 or bech32m (and correct HRP for network).

Examples

Error handling

When converting from this profile’s CAIP-2 encoding to this profile’s CAIP-350 encoding, the chain reference is already fully specified (32 hex chars), so no loss of information or difference of expression occurs. For addresses, invalid or unsupported native encodings (e.g. legacy P2PKH excluded from CAIP-10) should be rejected with an appropriate error.

Implementation considerations

Legacy P2PKH addresses are excluded from CAIP-10 and therefore from this profile. Only P2SH, SegWit, and Taproot address types are supported. Implementations must use the correct HRP and version bytes per network (e.g. mainnet vs testnet, or other BIP122 chains).

References

Citation

Please cite this document as:

Orca, Mono, "namespaces/bip122-caip350: BIP122 Namespace - Interoperable Address [DRAFT]," Chain Agnostic Namespaces, bip122-caip350, January 2026 / . [Online serial]. Available: https://github.com/ChainAgnostic/namespaces/bip122-caip350.md