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Fig. 4 URN v/s DID example

• urn: < namespace > : < identifier >

Here, the preceding characters of the first “:” indicate the scheme being used. This

would be “urn” for all URN-based identifiers. The next part of the URN denotes the

namespace (for example, “fruit” or “animal”). This is a common subtype to group

the entities to be identified. Following the second “:” is the actual identifier of an

entity (for example, “mango” or “dog”, respectively). UUIDs would have a structure

as shown below:

• urn:uuid: < 128 bit identifier in hexadecimal >

When it comes to DIDs, the format remains similar except, in this case, the scheme

changes, and the second part of the sequence between the colons denotes the protocol.

The protocol in the case of DIDs defines the type of blockchain platform (there is a

common misconception that Bitcoin is a “currency” when in fact it is the protocol

that governs a token). DIDs rely on a Key Management System as well, which is

cryptographically secure [30]. Figure 4 shows a common example of a DID and the

basic difference between a UUID and a DID.

In Table 1, we mention some of the common decentralized identifiers under

research and development by the community along with their respective desig-

nated DID prefixes. These are correct at the time of writing so please refer to their

actual implementation-wise prefixes in case of a version change or community-wide

adoption decision from W3C. Figure 4 illustrates an example of URN v/s DID.

3.2.3

Self-sovereign Identity (SSI)

Self-sovereign identity (SSI) is the concept where the individual has control over

their identity. SSI tends to the trouble of setting up a trust in a connection. To be