Decentralized Identifiers (DIDs)

Decentralized Identifiers (DIDs) are a cornerstone of the ArcBlock ecosystem, providing a universal and unique addressing system for virtually any entity on the blockchain. Unlike traditional systems where identifiers are limited to users, ArcBlock extends DIDs to represent accounts, tokens, NFTs, applications, and more. This approach creates a cohesive and interconnected digital environment.

These DIDs are designed to be compatible with the W3C DID Core specification, ensuring they are built on open standards. Understanding how DIDs are structured and generated is fundamental to interacting with other core concepts like Wallets and Accounts and Non-Fungible Tokens (NFTs).

DID Notation#

A typical DID on the ArcBlock platform follows a standardized format. Here is an example:

did:abt:z1muQ3xqHQK2uiACHyChikobsiY5kLqtShA

This string can be broken down into three parts:

Part	Example	Description
Scheme	did:	A standard prefix indicating that this is a DID.
Method	abt	Specifies the ArcBlock DID method.
Method-Specific ID	z1muQ3...	The unique identifier string, generated using a flexible set of cryptographic algorithms.

While other blockchains like Bitcoin and Ethereum use fixed hashing algorithms (e.g., secp256k1) to generate addresses, ArcBlock allows developers to choose the combination of algorithms for public key encryption, hashing, and encoding. This information is embedded directly into the DID itself.

DID Type#

The flexibility of ArcBlock DIDs is encoded within the "DID Type," a 2-byte (16-bit) segment at the beginning of the DID's binary representation. This type information specifies the exact combination of algorithms used to generate and secure the DID.

The 16 bits are allocated as follows:

For example, a DID type of 0x0C01 is interpreted as:

Binary	Hex	Value	Interpretation
000011	0x03	3	RoleType: ROLE_APPLICATION
00000	0x00	0	KeyType: ED25519
00001	0x01	1	HashType: SHA3

This embedded information makes each DID self-describing, allowing any system to understand how to interact with it without needing out-of-band configuration.

DID Generation Algorithm#

The process of creating a DID from a secret key involves a series of cryptographic steps. The following diagram illustrates the workflow:

This multi-step process, which includes a checksum, ensures that DIDs are not only unique but also verifiable and resistant to transcription errors.

Appendix: Type Definitions#

The following tables provide a comprehensive list of the available types that can be combined to create a DID. These are derived from the core protocol definitions.

RoleType#

RoleType defines the intended purpose of the DID.

Name	Value	Description
ROLE_ACCOUNT	0	Represents a user or entity account.
ROLE_NODE	1	Represents a node in the network.
ROLE_DEVICE	2	Represents a device.
ROLE_APPLICATION	3	Represents an application.
ROLE_SMART_CONTRACT	4	Represents a smart contract.
ROLE_BOT	5	Represents an automated agent or bot.
ROLE_ASSET	6	Represents a non-fungible asset (NFT).
ROLE_STAKE	7	Represents a stake transaction or state.
ROLE_VALIDATOR	8	Represents a validator node.
ROLE_GROUP	9	Represents a group of accounts.
ROLE_TX	10	Represents a transaction.
ROLE_TETHER	11	Represents a tethered resource.
ROLE_SWAP	12	Represents an atomic swap transaction.
ROLE_DELEGATION	13	Represents a delegation.
ROLE_VC	14	Represents a Verifiable Credential.
ROLE_BLOCKLET	15	Represents a Blocklet.
ROLE_STORE	16	Represents a store.
ROLE_TOKEN	17	Represents a fungible token.
ROLE_FACTORY	18	Represents a factory for creating assets or other entities.
ROLE_ROLLUP	19	Represents an ArcBridge (rollup) chain.
ROLE_STORAGE	20	Represents a storage service.
ROLE_ANY	63	Represents any role type.

KeyType#

KeyType specifies the cryptographic algorithm used for public/private key pairs.

Name	Value	Description
ED25519	0	Ed25519 signature algorithm.
SECP256K1	1	The algorithm used by Bitcoin and others.
ETHEREUM	2	An Ethereum-compatible key type.

HashType#

HashType defines the hashing function used in the generation process.

Name	Value	Description
KECCAK	0	Keccak hashing algorithm.
SHA3	1	SHA-3 (Secure Hash Algorithm 3).
SHA2	2	SHA-2 (Secure Hash Algorithm 2).
KECCAK_384	6	Keccak with a 384-bit output.
SHA3_384	7	SHA-3 with a 384-bit output.
KECCAK_512	13	Keccak with a 512-bit output.
SHA3_512	14	SHA-3 with a 512-bit output.

With a solid understanding of how DIDs function as the foundational identity layer, you are now ready to explore what these identities can create and own. To learn more, proceed to the next section on Non-Fungible Tokens (NFTs).