IRJET- A Survey on File Storage and Retrieval using Blockchain Technology

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 10 | Oct 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 763
A Survey on File Storage & Retrieval using Blockchain Technology
Yash Ranka1, Jainam Bagrecha2, Kavish Gandhi3, Bhargav Sarvaria4, Prof. P. M. Chawan5
1,2,3,4U. G. Student, Department of Computer Engineering and IT, VJTI College, Mumbai, Maharashtra, India
5Associate Professor, Department of Computer Engineering and IT, VJTI College, Mumbai, Maharashtra, India
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Abstract - Data drives business around the globe and is a
crucial aspect of the industry, which makes misuse of data
equally dangerous. Data needs to be stored and transferred
securely in order to maintain its confidentiality and
integrity. Ethereum platform and technologies like swarm
and whisper can make it possible to make a secured file
storage and retrieval Decentralized Application (DApp).
With the help of blockchain we propose an architecture
which is much safer and easier for human use and it also
solves the existing data storage and retrieval difficulties.
Key Words: Blockchain, Swarm, Whisper, Ethereum,
File Storage & Retrieval, P2P, IPFS, ENS
1. INTRODUCTION
A blockchain is a chain of blocks, where each block
contains a set of records (transactions) and the blocks are
linked using cryptography[1]. Blocks hold batches of valid
transactions. The transactions are hashed and encoded
together into a Merkle tree. Every block includes the
cryptographic hash of the previous block in the blockchain
which links and creates a chain of blocks. The linked
blocks form a chain. This iterative process confirms the
integrity of the previous block, all the way back to the
original genesis block.
There are many applications of blockchain viz.
Cryptocurrency, to secure Internet of Things, smart
Contracts based transactions. One promising application
of blockchain is File Transfer (Storage and Retrieval),
which can be implemented using Peer-to-Peer network,
Directed Acyclic Graph, Distributed Hash Table.
2. EXISTING TECHNOLOGIES
2.1 Distributed File System
Traditional file storage on a single computer can
be made more efficient using Distributed File System
(DFS) [2]. Data which is stored on a single
computer can be split and stored on multiple independent
computer (nodes). DFS makes file storage reliable by
allowing an user to retrieve data even when one or more
nodes of the network goes down, the data is replicated on
several nodes which increases availability of data, only
authenticated users can store and retrieve data from DFS
which makes it more secure and if the system runs out of
space we can add more nodes to the system which makes
DFS scalable.
Fig -1: DFS Architecture
A file is split into metadata and its content and
stored on the system while uploading. When a user wishes
to download the same file, he provides the Meta
information and the file is retrieved from multiple nodes
and provided to the user, this makes it appear as a single
coherent system for the user. Thus for a user it appears to
be stored as it were being stored on his own computer.
Thus DFS is reliable, scalable, secure and more available
but reduces the time of access for a file. DFS requires
algorithms for synchronization, locking and maintaining
data consistency.
2.2 InterPlanetary File System
The InterPlanetary File System (IPFS) [3] is a peer-to-
peer distributed file system that seeks to connect all
computing devices with the same system of files. The file is
divided into small blocks, the block is then hashed and
distributed across the IPFS network. The redundant
information is removed because the hashes are same for
similar files. IPFS provides a high throughput content-
addressed block storage model, with content-addressed
hyperlinks. A generalized Merkle DAG (Directed Acyclic
Graph), which can be used to build versioned file systems,
blockchain, etc. A distributed hash table, an incentivized
block exchange, and a self-certifying namespace is used by
IPFS. There is no point of failure in IPFS and it is not
necessary for the nodes to trust each other.

Fig -2: Overview of IPFS
2.3 Secured File Storage and Retrieval using
Blockchain
One of the simplest way to store/retrieve files is
to upload the file directly in the blocks of a blockchain. The
complexity to verify a block is directly proportional to the
size of the block and hence, larger file size will lead to
bigger blocks which eventually makes the network
inefficient with high latency. Though the file remains
secured because of decentralized nature of blockchain, we
cannot use it practically.
2.4 Storing the hashes of files on Blockchain
One way to increase the efficiency of the file
storage/retrieval is to use the hash of the file on the
blockchain instead of using the blocks of file. It further
provides auditable accountability of exactly what content
has been authorized by whom for sharing and transfer
through the file transfer guard. Continuous updating the
ledger for every file transfer gives an immutable record of
the entire life cycle of file. [4]
Fig -3: Storing hashes on Blockchain
2.5 Filecoin
Filecoin [5] is a kind of cryptocurrency where
individual data providers are provided with incentives for
their storage resources for storage of data pieces in the
filecoin network. The incentives are given based on the
amount of resources shared by the individual. Large
number of such individuals form a global distributed
network that runs filecoin protocol for file storage. The
contributing users may opt out if they wish and yet the
availability of the data is maintained by the distributed
network.
Filecoin makes use of two kinds of nodes: Storage
nodes & Retrieval nodes. The file is first encrypted and
then segments of the file are distributed to storage nodes.
The retrieval nodes need to be near the storage nodes so
that the transfer of data is fast. Only the authorized person
can retrieve it using her private key.
2.6 Storj
A peer-to-peer (P2P) cloud storage network
which uses client-side encryption allows users to transfer
and share data without depending on a third party storage
provider. Data availability is a function of popularity,
rather than utility which makes the P2P networks
unfeasible for production storage systems. A solution in
the form of a challenge-response verification system
coupled with direct payments is used by Storj [6].
The file is encrypted and sharded. The shards are
then distributed over a decentralized network of storage
nodes which are known as “farmers”. The data owners are
responsible for everything from pre-processing shards to
collecting them, managing file encryption keys, etc.
2.7 Decentralized file transfer using Multichain
framework [7]
This is a file transfer system where the receiver
first sends a request message to the sender with body as
burn address and its public key via email or facebook. The
RSA 2048 algorithm is used to generate public-key
private- key pair. The file is encrypted using Advanced
Encryption Standard (AES) and the public key. Then the
encrypted file is sharded into fixed size blocks and then
encoded using Hex encoding algorithm. The encoded parts
and the RSA public key is then stored on a private
blockchain. At the receiver’s end, the different blocks of
file are decoded using hex decoding and merged together.
The merged file is decrypted using the private key (of the
respective public key) and AES to produce the desired file.
[8]
3. PROPOSED SYSTEM
Our primary aim lies in solving the problem of
decentralized data storage, restricted data access and
preventing data redundancy using peer-to-peer network
storage clubbed with blockchain technology. The proposed

tech stack for the same includes Ethereum[9] swarm[10]
for data storage, distribution and retrieval over the
network, Ethereum whisper[11] protocol for sharing
access rights by the file owner and various Asymmetric
cryptographic algorithms along with data compression
algorithms for maintaining data confidentiality and
efficient data storage. The process is as follows:
We take the file which user needs to upload and encrypt it
using a new public-key private-key pair which will be held
by the file owner. The Asymmetric encryption technique
can help ensure the read-write access privileges. The user
with just public key can have read access and the user
with private key can have write access. Symmetric
encryption algorithms can also be used as per the
requirements. Once the file is encrypted it is further
processed for data compression using a predefined data
compression algorithm for efficient file storage. The
compressed and encrypted file is then distributed over the
swarm network and a unique hash for the file is calculated
by the swarm protocol through which the file can later be
accessed.
Once the file is distributed over the swarm network, the
generated hash for the file is then added to the blockchain
as a transaction to preserve the file integrity. Thus we
record the hash of the file by uploading it on the
blockchain.
Once the hash of the file is recorded on the blockchain, the
file owner can then decide to grant access privilege to
various other users using a messaging protocol- Ethereum
Whisper. The owner needs to send the file hash along with
the public key of the encrypted file by which the other
user will be able to decrypt the encrypted file and hence
access it and the entire message is encrypted using the
receiver’s public key, making the message unintelligible
for others.
The receiver can then decrypt it using her private key.
Thus even if someone tries to access the encrypted file by
fetching the file hash from the public blockchain she won't
be able to decrypt the file without the key. Thus,
preserving the confidentiality.
The problem of data redundancy has been automatically
solved as we calculate a unique hash for each file. Thus, if
we have two exactly same files both files will effectively
produce the same hash thus solving the redundancy
conflicts.
To make the file system more human-readable we make
use of the Ethereum Name Server (ENS). ENS works the
same way as the Domain Name Server, it effectively stores
the mapping of file hashes with the human readable
filenames using distributed hash tables. Thus the hashes
can be uniquely named as per the user convenience. Along
with improving readability, ENS serves an important
purpose. Generally the files stored this way are immutable
and static in nature as a slight change in file content would
effectively produce a new hash which will again increase
the redundancy of the network. ENS solves this by efficient
mapping from old files to new files, thus adding up more
to the user convenience. ENS can also be used to maintain
version control (like git).
The above process considers file uploaded to be the one
with limited access where the file owner shares the access
permissions with the limited set of users. However, some
files could be made available to general public where we
do not need to specify the access permissions. Such files
can be directly compressed and stored over the network.
The users who wants the access of such public files can
directly access it on the blockchain via some blockchain
explorer that searches for file hashes on the blockchain. To
make it more convenient for users such files can be
explicitly marked as public with the help of ENS.
Fig -4: Proposed System Architecture
4. CONCLUSION
In this paper we proposed an enhanced mechanism for
data storage and transfer. The whole mechanism uses
cryptography, blockchain and ethereum technology to
carry out the task as opposed to older mechanisms. The
given mechanism will make the task more secure through
cryptography, maintain data integrity through hash codes
and data readily available with decentralized data storage
on multiple hosts.
REFERENCES
[1] Blockchain-Wikipedia
“https://en.wikipedia.org/wiki/Blockchain”
[2] Pavel Bžoch - “Distributed File Systems”,
“https://www.kiv.zcu.cz/site/documents/verejne/vy
zkum/publikace/technicke-zpravy/2012/tr-2012-
02.pdf”
[3] J. Benet, “IPFS - content addressed, versioned, P2P file
system, (2014)”,
“https://github.com/ipfs/ipfs/blob/master/papers/i
pfs-cap2pfs/ipfs-p2p-file-system.pdf”

[4] Securing your cross-domain file transfers with
blockchain,
“https://www.ibm.com/blogs/blockchain/2018/05/s
ecuring-your-cross-domain-file-transfers-with-
blockchain/”
[5] Filecoin: “A Cryptocurrency Operated File Storage
Network” , “https://filecoin.io/filecoin-jul-2014.pdf”
[6] Storj - A Peer-to-Peer Cloud Storage Network,
“https://storj.io/storj.pdf”
[7] Dr Gideon Greenspan, “MultiChain Private
Blockchain”,
“https://www.multichain.com/download/MultiChain-
White-Paper.pdf”
[8] SriBalaji, Vignesh Mohan, Soundarya, “Secure and
Decentralized File Transfer Application using
Blockchain” ,
“http://troindia.in/journal/ijcesr/vol4iss4/169-
175.pdf”
[9] Vitalik Buterin, “Ethereum” , “https://ethereum.org/”
[10] Ethereum Swarm, “https://swarm-
guide.readthedocs.io/en/latest/introduction.html”
[11] Ethereum whisper,
“https://github.com/ethereum/wiki/wiki/Whisper-
PoC-2-Protocol-Spec”

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