A Survey of Attacks on Blockchain Technology

Öz

In recent times, popularity of blockchain based crypto currencies (bitcoin and ethereum) have been increased.  Blockchain system has decentralized peer to peer (P2P) network, all transactions are recorded in a public ledger that can only be appended.  The miners constitute the nodes of this network and every miner has local copy of ledger. In blockchain, PoW consensus algorithm is used to verify transaction and give permission to append new blocks to chain. To get reward, miners compete with each other to complete transactions on the peer to peer network. The reward system popularized Bitcoin, which uses block-chain, but at the same time attracted the atention of the attackers in the block chain. In this paper, current attacks against the block-chain are presented. In the first part, attack types to P2P architecture, consensus protocol and transaction are investigated. In this part, 51%, Double Spending, Finney, Vector76, Brute Force, Sybil, Eclipse and Balance attacks are explained and solutions are proposed. In addition, pool mining attacks such as block withholding attack (BWH), Pool hoping attack, Blacklisting via Punitive Forking, Feather Forking and bribery attack are presented.  In the last part, the future of cryptography used in blockchain infrastructure has been discussed and effects of Post Quantum Cryptography have been mentioned

Anahtar Kelimeler

• blockchain,security,bitcoin,ethereum

Blok Zinciri Teknolojisine Yapılan Saldırılar Üzerine bir İnceleme

Öz

Son zamanlarda;  blok zinciri tabanlı kripto para ödeme sistemleri(bitcoin, ethereum) oldukça popüler olmuştur. Merkezi olmayan eşler arası(P2P) ağ yapısına sahip olan bu sistemde tüm işlemler, sadece ekleme yapılabilen bir ana defterde(ledger) tutulmaktadır. Madenciler ise bu ağ yapısındaki düğümleri oluşturmaktadır, her madenci defterin yerel kopyasına sahiptir. Blok zincirinde, PoW uzlaşma protokolü işlemi onaylamakta ve zincire yeni blok eklenmesine izin vermektedir. Ödülü almak için, madenciler eşler arası ağda işlemi tamamlamak için birbirleriyle yarışırlar.  Ödül sistemi, blok zinciri kullanan bitcoin’i popülerleştirmiş,  fakat aynı zamanda saldırganların blok zincirine ilgisini artırmıştır. Saldırganlar tarafından blok zincirinin madenci havuzuna ve ağ yapısının güvenliğine farklı saldırılar yapılmıştır. Bu makalede, blok zinciri alt yapısına karşı mevcut saldırılar sunulmuştur. İlk bölümlerde, P2P mimarisine, uzlaşma protokolüne ve işlemlere yönelik saldırı tipleri araştırılmıştır. Bu bölümde, %51 saldırısı, Çift harcama, Finney, Vector76, Kaba Kuvvet, Sybil, Eclipse, Denge gibi saldırılar açıklanmış ve çözümler önerilmiştir. Daha sonra, Bencil madencilik ve Blok Atma, Blok Tutma(BWH),  Blok Tutma Sonrası Çatallanma(FAW), Havuz sıçrama saldırısı, Cezalandırıcı Çatallanma ile Kara Listeye Alma, Köpük saldırısı ve Rüşvet Saldırısı gibi madencilik havuzuna karşı saldırılar incelenmiş ve savunma stratejileri sunulmuştur. Son bölümde de blok zinciri altyapısında kullanılan kriptografi’nin geleceği üzerinde tartışılmış ve Post Kuantum Kriptografi’nin  etkilerinden bahsedilmiştir

Anahtar Kelimeler

• blok zinciri,güvenlik,bitcoin,ethereum

Kaynakça

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