  The challenge to establish and verify human identity over the Internet in a
secure and privacy-respecting way is long-standing. In this paper, we explore
the blockchain trilemma of scalability, security, and decentralization in the
context of the Trust Registry: a root of trust for a decentralized identity
scheme that enables read and write access to shared records and is
tamper-resistant. We make a case study of Hyperledger Indy -- an open-source
technology bespoke for decentralized identity -- and conduct two empirical
experiments to measure the latency of more than 45,000 transactions in the
naturalistic environment of Amazon Web Services. We conclude that issues of
Trust Registry scalability have multiple facets. While Hyperledger Indy
captures data useful to underpin a decentralized identity scheme, the knock-on
effect of its scalability limitations may indeed place constraints on
properties of security and decentralization. The current credential
verification process relies on transaction processing by a ledger with
transaction processing bottlenecks, which may constrain the ideal of
non-repudiation.
