IEEE Electrification - September 2021 - 48

An important component of blockchain technology is
the use of cryptographic hash functions. Applying a
cryptographic hash function to data calculates a unique
output for an input of nearly any size (e.g., a text, file, or
image). Even a small change to the input (e.g., changing
a single bit) will result in a completely different hash
output. A specific cryptographic hash function used in
many blockchain implementations is the secure hash
algorithm (SHA), with an output size of 256 bits (SHA256)
displayed as a 64-character hexadecimal string.
Although there are an infinite number of possible input
values and a finite number of possible output values, it
is highly unlikely to have a collision where hash(x) =
hash(y) (i.e., the hash of two different inputs produces
the same output). This property of hash functions is
referred to as collision resistance. To find a collision in
SHA-256, one would have to execute the algorithm, on
average, roughly 2128 times, i.e., approximately 3.402 ×
1038 tries. To put this into perspective, it would take the
entire Bitcoin network roughly 3.6 × 1013 years (more
than the estimated age of the universe) to manufacture
a collision (Yaga et al. 2018). However, with the rise in
quantum computing and an increase in transaction
rates, the collision resistance of current hash algorithms
are declining and new more collision-resistant algorithms
are emerging.
Digital signatures employ asymmetric cryptography,
i.e., a cryptographic system that uses a pair of keys, namely,
a public key, which may be shared widely, and a private
key, which is known only to the specific owner, to encrypt
and decrypt messages. A private key is used to encrypt a
transaction such that anyone with the public key can
decrypt it. Encrypting the transaction with the private key
proves that the signer of the transaction has access to the
private key. Similarly, one can encrypt data with a user's
public key such that only the users with access to the private
key can decrypt it.
The data written to a blockchain cannot be edited, even
by a system administrator. This is referred to as blockchain
immutability and ensures that sent and received data and
transactions cannot be altered. Any " corrections " to a prior
transaction must be accomplished by a new reverse transaction
that is subjected to validation before getting added
to the blockchain.
A " node " within a blockchain network includes the
hardware, software, communications, and data of a blockchain
network participant. The blockchain nodes may
generally be classified into three categories:
x Full node: a node that stores the entire blockchain and
ensures the validity of transactions
x Publishing node: a full node that also publishes new
blocks
x Lightweight node: a node that does not store or maintain
a copy of the blockchain and must pass its transactions
to full nodes.
Blockchain network users submit candidate transactions
to the blockchain network via software from their
respective nodes to other nodes. The transactions are
added to the blockchain when a publishing node publishes
a block.
The new blocks can only be added at the open end of
the chain by participating nodes following rules set in the
Bulk Power Markets
T-DSP
Energy Service Providers
Aggregators
DER Providers
Prosumers
Microgrids
T-DERMS
Forecasting
VPP Management
Economic
Optimization
Distribution Constraint
Management
Scheduling and Dispatch
Data Acquisition and Control
(IoTSCADA)
DR
Assets
DER
Assets
µG
Assets
Grid
Assets
Bulk Power
Market Interfaces
Master
Data Management
Utility
Operations Interfaces
Registration
and Qualification
Hosting Capacity and
Interconnection Request
Management
Performance Monitoring
and Settlements
Metering
Figure 1. A T-DSP (with no blockchain). T-DERMS: transactive distributed energy resource management system; IoTSCADA: Internet of Things
supervisory control and data acquisition; VPP: virtual power plant; DR: demand response.
48
IEEE Electrification Magazine / SEPTEMBER 2021
Distribution Operations
Customer Services
Distribution Planning
Participant Interfaces
Transactive Operations
IEEE Electrification - September 2021

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