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Ensuring Data Integrity Using Blockchain
Technology
Igor Zikratov, Alexander Kuzmin, Vladislav Akimenko, Viktor Niculichev, Lucas Yalansky
ITMO University
Saint-Petersburg, Russia
zikratov@cit.ifmo.ru, akouzmin@altirix.ru, yavlad96i@gmail.com, mail@nikva.ru, yal@tuta.io
Abstract—Blockchain is a relatively new technology that has
shown a lot of possibilities. It emerged in 2009 as a public ledger
of all Bitcoin transactions. Blockchain technology is finding
applications in wide range of areas: digital assets and stocks,
smart contracts, record keeping, ID systems, cloud storage, ride
sharing, etc. We investigate the blockchains’ activity in terms of
how to store, retrieve and share files in decentralized network.
I. INTRODUCTION
Many people are excited about cryptocurrencies like
Bitcoin, but what is even more interesting is the technology
that powers it.
A blockchain is essentially a distributed database of
records, or public ledger of all transactions or digital events
that have been executed and shared among participating
parties. Each transaction in the public ledger is verified by
consensus of a majority of the participants in the system. Once
entered, information can never be erased. The blockchain
contains a certain and verifiable record of every single
transaction ever made.
Beyond currency, the blockchain can be used in smart
contracts, record keeping, ID systems, cloud storage and many
other areas.
In our study we decided to look closely at how to ensure
data integrity using blockchain technology.
The Clark-Wilson model identified the features of an
integrity-secure system. It consists of the following factors:
well-formed transactions, separation of duty, authentication,
audit, Principle of least privilege, objective control and control
over privilege transfer [1].
We are mostly interested in creating our own version of
private chain IaaS “Zeppar”, that is similar to Storj and
BigchainDB, except for the effort of ensuring data integrity in
the process. Our model quantifies the importance of several
factors that determine data integrity formulated by Clark and
Wilson including well-formed transactions, separation of duty,
authentication, audit, Principle of least privilege, objective
control and control over privilege transfer.
II. RELATED WORKS
Users of cloud systems commonly assume that if their data
is encrypted before outsourcing it to the cloud, it is secure
enough. Although encryption is to provide solid
confidentiality against internal attacks, it does not protect that
data from corruption caused by configuration errors and
software bugs. There are two traditional ways of proving the
integrity of data outsourced in a remote server. Checking the
integrity of data can be by a client or by a third party. The first
one is downloading the file and then checking the hash value.
In this way, a message authentication code algorithm is used.
MAC algorithms take two inputs, which are a secret key
and variable length of data, which produce one output, which
is a MAC. In this way this algorithm is run on the client side.
After getting a MAC, the data owner outsources those data to
the cloud. For checking its integrity, the data owner downloads
the outsourced data and then calculates the MAC for it and
compares it with the one calculated before outsourcing that
data.
By using this method accidental and intentional changes
will be detected. Also, by using the key, the authenticity of
data will be protected and only the one who has the key can
check the data authenticity and integrity. For a large file,
downloading and calculating the MAC of the file is an
overwhelming process and takes a lot of time. Also, it is not
practical since it consumes more bandwidth.
Therefore, there is a need for using a lighter technique,
which is calculating the hashing value. The second one is to
compute that hash value in the cloud by using a hash tree. In
this technique, the hash tree is built from bottom to top where
the leaves are the data and parents are also hashed together
until the root is reached. The owner of data only stores the
root. When the owner needs to check his data, he asks for just
root value and compares it with the one he has. This is also to
some extent is not practical because computing the hash value
of a huge number of values consumes more computation.
Sometimes, when the provided service is just storage without
computation, the user download the file, the same as in the
first case, or send it to third party, which will consume more
bandwidth.
Therefore, there is a need to find a way to check data
integrity while saving bandwidth and computation power.
Remote data auditing, by which the data integrity or
correctness of remotely stored data is investigated, has been
given more attention recently.
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A. Third Party Auditor
Third Party Auditor (TPA) is the person who has the skills
and experience to carry out all auditing processes. TPA
scheme is used for checking the data integrity. Architecture of
third-party auditing their proposed scheme attains data
integrity and assures the data owner of the data security. The
owner is aware of all his resources on the cloud. Therefore,
this scheme guarantees the integrity of data for all owner
resources on the cloud.
This scheme involves the data owner in the auditing
process. First, TPA uses normal auditing processes. Once they
discover any modification to the data, the owner is notified
about those changes. The owner checks the logs of the
auditing process to validate those changes. If the owner
suspects that unusual actions have happened to his data, he can
check his data by himself or by another auditor assigned by
him.
Therefore, the owner is always tracking any modification to
his own data. There is an assigned threshold value that a
response from the third party auditor should not exceed. The
data owner validates all modifications lesser than or equal to
this threshold. If the time exceeds this threshold, the data
owner is supposed to do surprise auditing
Fig. 1. TPA-method
The disadvantages of this method are the need for third-
party communication channel, as well as the exposure of the
"man in the middle" attacks. In addition, the emergence of a
third party for data processing, this increases the risk of the
implementation of a range of threats from hackers [2].
B. Provable Data Possession (PDP) and related methods
Provable Data Possession (PDP) scheme to investigate
statically the correctness of the data outsourced to cloud
storage without retrieving the data. In the proposed model is to
check that data stored in a remote server are still in its
possession and that the server has the original data without
retrieving it. This model is based on probabilistic proofs by
randomly choosing a set of blocks from the server to prove the
possession.
They used a RSA-based homomorphic verifiable tag,
which is combines tags in order to provide a message that the
client can use to prove that the server has specific block
regardless of whether the client has access to this specific
block or not [3].
Fig. 2. Pre-process of PDP-protocol
At a pre-process step, before sending files to the cloud,
user modifies data and adding metadata, at the same time
maintaining in the client metadata repository.
In the future, when checking the fact of the immutability of
the file saved in the cloud, the user generates a request to the
server to store file metadata comparison to the repository
metadata repository located in the client [4].
Fig. 3. Checking of PDP-protocol
A further development of the method is the E-PDP, which
is different protocol capable of 185 times faster and generate
metadata file, in fact, only limited operating speed
reading/writing physical storage devices. There are also
variations in the method of the PDP, such as Proof of
Retrievability (POR), and the method of Prof. Ownership,
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The main disadvantage of the above methods is the need
for the metadata store on the user side, which increases the
number of potential targets for an attack. In addition, these
methods make it very difficult to ensure the integrity of the
dynamic files.
Cloud Storage consists of a set of virtual machines. This
can be successfully applied for blockchain.
Fig. 4. Blockchain ensure data integrity method in Cloud Storage
Blockchain is a structure composed of blocks each of
which are recorded transaction. The box consists of a header
and the transaction list. Title block includes a hash, hash of the
previous block, the transaction. Transaction, inter alia,
contains an attribute within the input link to the transaction
with the previous state data. As a result of the hash is
irreversible, there is no algorithm for obtaining the desired
result, in addition to random search. The node sends the
resulting unit is connected to other nodes that test unit. If there
are no errors, then the block is considered to be added to the
chain, and the next block should include a hash of it.
Eligible units are sent to the network joining in a
distributed database blocks. Regularly there are situations
when a number of new units in different parts of the
distributed network called the previous one and the same unit,
ie, the chain may branch blocks. Intentionally or accidentally,
you can restrict relaying information about the new blocks (for
example, one of the chains can be developed within the local
network). In this method the possible build-up of various
parallel branches. Each of the new block can occur as the same
transaction, or different, included in only one of them. In
method of equal complexity and length of that preference is
given to the chain, the end of which there was previously a
block.
Chain blocks contains the history of ownership, which can
be found. Cloud storage generally is a cluster is divided into
virtual spaces allocated to each individual user. Functionality
of the proposed method consists of two main parts: the part
that is responsible for the formation of user transactions and
the part that is responsible for maintenance of the transaction
block chain. The method is applicable to both static files and
dynamic. If the static files are immutable and are available for
downloading or rewriting.
Thus, for a static file changes fact serves only its full
rewriting. Recording a transaction takes place in a block using
the method of concurrent access without locks. Separation of
access between threads comes at the expense of atomic
operations for each of the file types. There are three types of
transactions: the creation, modification, deletion. If part,
responsible for the formation of user transactions, finds that
the file is modified, the transaction is created in which is
specified the current hash of the file and the previous one.
Previous hash is taken from the block chain ,. When creating /
deleting a file created by the transaction, where the value of
the previous / current hash take special values.
Working with dynamic files. The user writes various
dynamic files, such as databases. Then he sets up the
configuration file of a background process that monitors the
change in dynamic files. When you first start a transaction file
is created with the original hash file and sent to the server. It
then monitors data files for changes. If changes are made
unauthorized process that sent the notification to the user.
Otherwise, at user-defined intervals updated hashes of the
files. Concurrent user access to dynamic files is carried out by
internal application modules working with dynamic files.
One of the main components of this method is that the
virtual machine is engaged in transaction processing blocks
chain. She receives a transaction from client programs,
background, checks for validity. Notification of non-valid
transactions, the creation of units of valid transactions, the
spread of new units through the network of virtual machines.
III. RELEVANCE
Is blockchain relevant?
Blockchain technology is being used in all types of
industries. This is not surprising because this technology
provides a wide range of different features and amenities.
Some examples are:
Ɣ Scaling
Ɣ Monitoring the chain in real-time (event-based
triggers)
Ɣ User isolation
Ɣ Momentary asset transfer over the network
Ɣ Immutability
Ɣ Modular core
Having assessed all the advantages of this technology. it
becomes obvious that it can be used to monitor the integrity of
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files, which is one of the most important tasks of information
security.
IV. OVERVIEW
Our method is divided into two main parts: the frontend
and server. The frontend consists of the UI and programs that
implement the services provided by the server. The server is
responsible for processing the transactions,
creating/transmitting blocks and handling all user access
control.
A. Frontend
The user interface is a web application which provides the
user the ability to access the provided storage space
(uploading/downloading data).
B. Backend
The backend is the core of our system. It is where all of our
services that ensure data integrity of the file storage are
implemented.
The backend consists of several parts.
1) ABRAXAS
ABRAXAS uses the FileSystemWatcher class to get
notifications from the OS about changes in the filesystem. It
then creates and sends the transactions based on the data that
the OS provides. ABRAXAS creates and sends transactions.
Transactions can be of 4 different types, each one
corresponds to a different filesystem operation. The
transactions are standardized:
Ɣ Tx Type: identifies the type of the transaction.
Actual Hash: current hash of file
Ɣ Prev Hash: previous hash of file
Ɣ Timestamp: the exact time and date when the
transaction was created in UNIX-time.
Ɣ Previous/Current Path: previous/current path to file
Ɣ Signature: digital cryptographic signature of the file
owner.
Types of transactions:
a) OnCreated
This type of transaction is formed when a file is created.
Fig. 5. Transaction scheme of OnCreated type
b) OnChanged
This type of transaction is sent when a file is changed.
Fig. 6. Transaction scheme of OnChanged type
c) OnDeleted
This type of transaction is sent when a file is deleted.
Fig. 7. Transaction scheme of OnDeleted type
d) OnRenamed
This type of transaction is sent when a file is renamed.
Fig. 8. Transaction scheme of OnRenamed type
2) A worker process processes the transactions and
creates blocks out of them. [5]
Fig. 9. Scheme of Block
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V. MODEL DESCRIPTION
As mentioned earlier, there are two components of the
entire client system, is solely responsible for the use and
experience of the responsible for all computing processes and
ensuring the integrity of file storage. Now in more detail about
each of them.
A. User side
The user interface is a web application which provides the
user the ability to access the provided storage space
(uploading/downloading files).
B. Server side
1) Session management [6]
Session management is handled on the server [7].
Users can authenticate using a login/password pair, a
private/pub key pair or even a smart card.
Once authenticated, a session key is created by hashing a
random nonce with the username using the GOST R 34.11-
2012 (Stribog) algorithm. The session key will be used for all
server-side functions until it expires.
2) FileSystemWatcher
Algorithm 1 setWatchers
0: List<FileSystemWatcher> watchers = new
List<Filesystemwatcher> ();
1: configurations = getConfiguration(config)
2: foreach (Configuration conf in configurations) {
3: watchers..add(new
FileSystemWatcher(conf))}
4: return watchers.
3) Type of transactions
ȿhe basic idea was taken from creation Secure High-Rate
Transaction Processing in Bitcoin [8]
Algorithm 2 struct Transaction_FileChanged
0: public int OpCode;
1: public string OldFileHash;
2: public string NewFileHash;
3: public DateTime TransactionCreationTime;
4: public string signature;
Algorithm 3 struct Transaction_FileCreated
0: public int OpCode;
1: public string FileHash;
2: public DateTime TransactionCreationTime;
3: public string signature;
4: public string path;
Algorithm 4 struct Transaction_FileDeleted
0: public int OpCode;
1: public string FileHash;
2: public DateTime TransactionCreationTime;
3: public string signature;
4) Creation of transactions
Algorithm 5 createTransaction
0: Transaction t = new Transaction();
1: t.setOldFileHash();
2: t.setNewFileHash(getHash(e));
3: t.setTransactionCreationTime();
4: t.setSignature();
5: send(t);
5) Making block of transactions
Algorithm 6 createBlock
0: Block b = new Block();
1: foreach (Transaction t in tx) {
2: if (t.isValid) {
3: b.add(t)}
4: else sendnotification();}
6) Integrity check (Cross-checking hashes with blockchain).
As it mentioned in works [9].
Algorithm 6 checkIntegrity
0: hash = searchInBlockchain(file.Fullpath);
1: if (hash = gethash(file)) return true;
2: else return false;
VI. CONCLUSION
Blockchain technology can secure integrity of files stored
in the database. It can be achieved through well-formed
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transactions, authentication, audit that blockchain provides.
The amount of possible threats to data integrity can be
decreased.
With one of the three main security attributes secured
blockchain can be used in order to ensure the remaining two
properties of data: confidentiality and availability [8].
There are limitations of using blockchain as it relies on the
fact that it is mathematically impossible for a single party to
game the system due to lack of needed compute power.
However, with the advent of Quantum Computers, the
cryptographic keys may be easy enough to crack through brute
force approach within a reasonable time. This will destroy
blockchain technology [10].
REFERENCES
[1] Clark, D., Wilson, D. A compassion of Commercial and Military
Computer Security Policies (1987)
[2] Sultan Aldossary, William Allen. Data Security, Privacy, Availability
and Integrity in Cloud Computing: Issues and Current Solutions.
(IJACSA) International Journal of Advanced Computer Science and
Applications,Vol. 7, No. 4, 2016 pp.485-498
[3] Dr.Nedhal A.Al-Saiyd, Nada Sail. Data integrity in Cloud computing
security. Journal of Theoretical and Applied Information Technology.
31.12.2013. Vol. 58 ʋ3 pp. 570-581
[4] Giuseppe Ateniese, Randal Burns. Provable Data Possession at
Untrusted Stores. 14th ACM Conference on Computer and
Communications Security(CCS 2007)
[5] Tsirlov, L. Bases of information security of the automated systems.Short
course.Phoenix (2008)
[6] Wilkinson, S., Lowry J. Metadisk: Blockchain-Based Decentralized File
Storage. Application (2014)
[7] Sompolinsky, Y., Zohar, A. Secure High-Rate Transaction Processing in
Bitcoin (2015)
[8] Nakamoto, S.: Bitcoin: A peer-to-peer electronic cash system (2008)
[9] Zyskind, G., Nathan, O., Pentland, A. Decentralizing privacy: Using
blockchain to protect personal data (2015)
[10] Andy Majot and Roman Yampolskiy, 2015. Global catastrophic risk and
security implications of quantum computers. Futures, vol. 72
(September), pages 17-26.
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