agreement ledger (s.v. "Agreement Ledger"): A distributed ledger used by two or more parties to negotiate and reach agreement. (†2369)
attestation ledger (p.46 ; s.v. "Attestation register"): A distributed ledger providing a durable record of agreements, commitments or statements, providing evidence (attestation) that these agreements, commitments or statements were made. (†2370)
blockchain (p.46): (or blockchain technology). The generic name
for the family of technologies that provide the same
functionality as bitcoin, but which use different approaches
to realising the functionality, via alternate algorithms for
example, a family of solutions. (†2233)
Byzantine General's Problem (p.15): Computer scientists have long concerned themselves
with the problem of maintaining a consistent and
accurate set of records in a large and complex
computer system where malfunctioning components
give conflicting information to different parts of the
system, or where hacked components deliberately lie
in an attempt to subvert the system. Bitcoin is subject
to this problem because the integrity of the distributed
ledger must be maintained in an environment where
some of the miners may be actively working to subvert
the ledger. This problem is called the Byzantine
Generals’ Problem as it’s often described in terms of a
group of generals of the Byzantine army camped with
their troops around an enemy city.
· The problem is often formulated along the
following lines: ‘Reliable computer systems must
handle malfunctioning components that give
conflicting information to different parts of the system.
This situation can be expressed abstractly in terms of a
group of generals of the Byzantine army camped with
their troops around an enemy city. Communicating
only by messenger, the generals must agree upon a
common battle plan. However, one or more of them
may be traitors who will try to confuse the others. The
problem is to find an algorithm to ensure that the loyal
generals will reach agreement. It is shown that, using
only oral messages, this problem is solvable if, and
only if, more than two-thirds of the generals are loyal;
so a single traitor can confound two loyal generals.
With unforgeable written messages, the problem is
solvable for any number of generals and possible
traitors. Applications of the solutions to reliable
computer systems are then discussed.’
— Leslie Lamppost, Robert Shostak & Marshall Pease,
The Byzantine Generals’ Problem (†2231)
consensus mechanism (p.46): Consensus Process. The process a group of peers responsible
for maintaining a distributed ledger use to reach consensus on
the ledger’s contents. (†2234)
distributed ledger technology (p. 12): We can think of distributed ledgers as a consequence of the mass adoption of digital networks, and the logical evolution of physical ledgers (lines of text in a codex) and digital ledgers (rows in a database). Both physical and digital ledgers record entries in a single place; as a central agency is typically
responsible for them we might call them central ledgers. Central ledgers allow one authoritative copy of the data. For physical ledgers, this is a single codex, or a volume in a series. Digital ledgers use a single database, a system of record. (†2044)
distributed ledger technology (p.12): Distributed: Responsibility
for maintaining the ledger
shared by a group of peers.
The current state of the ledger
is represented by the peer’s
consensus on what records the ledger contains. Other
actors can obtain a copy of the ledger from any of the
peers, as there is no single authoritative copy. Other actors
can submit new records to any or all of the peers.
Ledger identity and integrity ensured via the consensus
process, that specifies how peers reach consensus. (†2229)
distributed ledger technology (p.16; s.v. "A definition" ): We therefore provide a definition of ‘distributed ledger’:
a ledger maintained by a group of peers, rather than a central agency.
· Any member of the group of peers can add records to the ledger. However,
records are only accepted when the group agrees the record meets all the
ledger’s requirements – typically it must be unique, correctly signed, etc.
· For a distributed ledger to be trusted, it must have two characteristics:
One, we must be confident the records it contains haven’t been tampered with.
We do this with cryptography via digital signatures, in much the same way we
sign other digital documents, and digital fingerprints using a technique called
‘hashing’, which is extremely sensitive to any change in underlying data. The use
of cryptography is what gave virtual currencies created on digital ledgers the
name ‘cryptocurrencies’. · Two, we must determine what records are stored in the ledger and their precedence
– the ledger’s contents. The consensus view of the group of peers represents
the contents of a distributed ledger. This consensus must be established in an
environment where we assume some of the peers are providing erroneous data. (†2230)
ledger (p.46): An append-only record store, where records are immutable and may hold more general information than financial records. (†2235)
permissioned blockchain (p.22): A permissioned ledger is a ledger where actors must have permission to access the ledger.
Permissioned ledgers map to closed trust-some or trust-all ledgers. Permission is granted in two different ways. The first is via a white list, a list of actors allowed
to join the ledger’s community. The second is via a black list, a list of actors who are banned from the ledger’s community: a permissioned ledger using a black list would be a closed, trust-some ledger; a permissioned ledger using a white list could be either
an open or closed, trust-some ledger. We note Bitcoin was originally designed to be
permissionless, although it is becoming increasingly permission-based as the various services enabling one to access the ledger demand you identify yourself– typically to comply with anti money-laundering or counter-terrorism financing regulations. (†2232)
replicated ledger (p.46 ; s.v. "Replicated ledger"): A ledger with one master (authoritative) copy of the data, and many slave (non-authoritative) copies. (†2371)
