Page 26 - ITU Journal - ICT Discoveries - Volume 1, No. 2, December 2018 - Second special issue on Data for Good

ITU JOURNAL: ICT Discoveries, Vol. 1(2), December 2018

physical objects on the Internet of things (IoT) or 4. DISTRIBUTED BLOCKS
other resource constrained enviroments, a local
time value may be the only possibility. Blockchain has been described as a promising
technique "to create a decentralized, peer-to-peer
A timestamp attribute can be defined as an trust network" [8]. Due to the success of Bitcoin, a
extensible pair of choice alternatives in ASN.1 as blockchain-based cryptocurrency, blockchain has
follows: emerged as a distributed platform capable of
providing a ledger for payments and other types of
timeStamped ATTRIBUTE ::= { transaction data. It is widely believed that
WITH SYNTAX TimeStamped ID id-TimeStamped blockchain will play an important role in securing
}
cyber physical systems, and that blockchain will be
TimeStamped ::= SEQUENCE { applied to Internet of things (IoT) applications
timeStampValue TimeStamp, from cloud computing to "home gateway" and
timeStampService URI OPTIONAL "edge computing" envionments [8].
}

TimeStamp ::= CHOICE { Part of the appeal of blockchain lies in its promise
timeStampToken TimeStampToken, to provide a secure design for supporting a
localTimeStamp GeneralizedTime, "distributed computing system with high

... -- Expect additional time types -- Byzantine fault tolerance", an efficient distributed
} system that can be operated "without depending
on a central authority" [8]. One property used to
A value of type TimeStamped contains two quantify the scalability of a blockchain architecture
components, a required timeStampValue and an is the "decentralization of block production (DBP)"
optional timeStampService. The timeStampValue [9]. This term has been defined as " the number of
component is a value of type TimeStamp, a choice block producers" [9].
between an X9.95 [7] trusted timestamp token,
and a value from a local time source. Trusted A set of SignedData blockchain blocks can be
timestamps can provide greater assurance of the distributed in whole, just as Bitcoin blockchains
validity of the ordering of block content. can be distributed. Additionally, in a SignedData
blockchain, each of the blocks can be separately
The optional timeStampService component of type distributed. Each block can be signed by a different
TimeStamped is a value of type URI. This value signer using a different signing key. The signer of
indicates the location of a timestamp authority each block can use a different message digest and
(TSA) that can issue and verify the timestamp signature algorithm, perhaps to meet specific
token. This component should be omitted when a industry or regulatory requirements.
local time source is used, or when the location of a
timestamp service is required but known as a Each block signer can include any number or type
system default. of signed attributes along with those required.
Each distributed block can serve as an independent
A TSA ensures that "an independent third party block producer. A SignedData blockchain can be
can audit and validate the controls over the use of extended with additional blocks, and each block
a time stamp process [7]. Unlike locally sourced can spawn a series of sidechains, blockchains
time that must be continuously synchronized by associated with a parent block. This capability
blockchain participants, a TSA relies on time allows SignedData blockchain users to create and
sourced from a national measurement institute manage flexible blockchain grids.
(NMI) or other "Master Clocks upstream from a
TSA that provides time calibration services" [7]. 5. SIDECHAINS
The time source for an NMI is the "Bureau
International des Poids et Mesures (BIPM) near 5.1 Defintions
Paris, France" which calibrates the NMI clocks used
to calibrate a TSA [7]. Many definitions of the term 'sidechain' come from
descriptions of blockchain architectures used to
transfer cryptographic currencies, such as Bitcoin
[4]. In their strong federation paper, Dilley,

4 © International Telecommunication Union, 2018