Malleability of the blockchain’s entropy

Trustworthy generation of public random numbers is necessary for the security of a number of cryptographic applications. It was suggested to use the inherent unpredictability of blockchains as a source of public randomness. Entropy from the Bitcoin blockchain in particular has been used in lotteries and has been suggested for a number of other applications ranging from smart contracts to election auditing. In this Arcticle, we analyse this idea and show how an adversary could manipulate these random numbers, even with limited computational power and financial budget.

[1]  Michael O. Rabin,et al.  Transaction Protection by Beacons , 1983, J. Comput. Syst. Sci..

[2]  Hugo Krawczyk,et al.  Randomness Extraction and Key Derivation Using the CBC, Cascade and HMAC Modes , 2004, CRYPTO.

[3]  S. Nakamoto Bitcoin: A Peer-to-Peer Electronic Cash System , 2008 .

[4]  Jeremy Clark,et al.  Scantegrity II: End-to-End Verifiability for Optical Scan Election Systems using Invisible Ink Confirmation Codes , 2008, EVT.

[5]  Jeremy Clark,et al.  Scantegrity II: end-to-end verifiability by voters of optical scan elections through confirmation codes , 2009, IEEE Trans. Inf. Forensics Secur..

[6]  Jeremy Clark,et al.  On the Use of Financial Data as a Random Beacon , 2010, EVT/WOTE.

[7]  Matthew Green,et al.  Zerocoin: Anonymous Distributed E-Cash from Bitcoin , 2013, 2013 IEEE Symposium on Security and Privacy.

[8]  Jeremy Clark,et al.  Mixcoin: Anonymity for Bitcoin with Accountable Mixes , 2014, Financial Cryptography.

[9]  Matthew Green,et al.  Rational Zero: Economic Security for Zerocoin with Everlasting Anonymity , 2014, Financial Cryptography Workshops.

[10]  Aggelos Kiayias,et al.  The Bitcoin Backbone Protocol: Analysis and Applications , 2015, EUROCRYPT.

[11]  Jeremy Clark,et al.  On Bitcoin as a public randomness source , 2015, IACR Cryptol. ePrint Arch..

[12]  Arjen K. Lenstra,et al.  A random zoo: sloth, unicorn, and trx , 2015, IACR Cryptol. ePrint Arch..

[13]  Aviv Zohar,et al.  Optimal Selfish Mining Strategies in Bitcoin , 2015, Financial Cryptography.

[14]  Joseph Bonneau,et al.  Why Buy When You Can Rent? - Bribery Attacks on Bitcoin-Style Consensus , 2016, Financial Cryptography Workshops.