Page 111 - Handbook of Deep Learning in Biomedical Engineering Techniques and Applications

Chapter 4 A critical review on using blockchain technology in education domain 99

Current index
Last index
Signature
Value
Timestamp
Nonce
Transaction hash
Branch hash
Trunk hash
Bundle hash
Figure 4.4 Transaction.

• Time efficiency attributed to the blockless structure of DAGs
• Supports smaller transactions due negligible transaction fees
Tangle is the consensus method in IOTA DAG. The various
steps in forming a DAG in Tangle include the following [13]:
(1) Creation of a bundle on arrival of a new transaction arrives
from a node.
(2) Transaction validation: The new transaction approves (vali-
dates) two previous transactions called as tips using tip selec-
tion algorithm. The node checks if the two transactions are
not conflicting to approve them.
(3) Preparation of a valid transaction bundle by the following:
a. Identifying input and output transactions
b. Identifying the attributes of a transaction that includes
(Fig. 4.4) the following:
a. Current index
b. Index of last transaction in the bundle
c. Create and sign the new transaction
d. Timestamp
e. The node must find the nonce by solving a crypto-
graphic hash function with a difficulty level specified
using leading zeros (PoW)
f. Create bundle hash using Kurl hash function and add to
each transaction
g. Fill in the branch and trunk transaction hash
(4) Broadcast of the new transaction bundle to the IOTA network.
A bundle account has a number of transactions. Each transac-
tion has its own address. For each account, a seed (81 character
long) is generated. From the seed, several pairs of cryptographic
keys (public and private) can be generated. A key segment k i is
generated by hashing the seed “i” times. This forms the private
key. If b i is bundle hash, then the key segment k i is hashed 13-b i
times to generate digital signature. This signature is embedded
in the corresponding output transactions to preserve the integrity.