Bitcoin is the first decentralized peer-to-peer and the most prominent cryptocurrency.
Cryptocurrency is a kind of digital currency, which is built on some cryptographic algorithms, and also it is called virtual currency.
Bitcoin was started to use in 2009.
Since 2009, it has had great interest, investment and contribution by developers and users. It was an alternative to fiat currency, which does not have any central authority to control money.
After Bitcoin successful attempt, many alternative coins have been emerged so far for different aims. Developers implemented many different versions of Bitcoin.
Some of them use a big portion of Bitcoin source code like Litecoin.
Some cryptocurrencies like Zcash, Ripple, Peercoin have been implemented to tackle some deficiencies of Bitcoin like privacy, scalability, energy consumption.
Somewere developed with innovative ideas by utilizing blockchain idea like Ethereum, Namecoin, Colored Coin. Every day, a new altcoin with different feature come to the market and it is believed that cryptocurrency will replace with fiat currency in the future.
In this thesis, Bitcoin and alternative coins called altcoins are discussed and compared according to some criteria like privacy, transaction malleability, scalability, attacks.
Future perspectives are discussed and some further work is planned for this comparative study.
