Purpose

The Ben-Or, Goldwasser, and Widgerson protocol ^[1] allows for multi-party secure function evaluation in an environment relying on:

• Honest but curious operation: Honest in that every party is obliged to follow the protocol. Curious in that all parties try to find out as much about the other parties as possible.^[2]
• Pairwise secure channels which exist between parties
• Synchronous communication: Each party waits until it receives all messages for a given round before sending messages for the next round.

Bitcoin allows shared ownership of coins by using multisignature transactions.

This guide walks thorugh:

• writing a multisignature transaction by hand
• broadcasting it to blockchain
• the practical applications of such a transaction

The RSA Conference 2019 Cryptographers’ Panel was probably the most legit panel I have ever had the privilege of attending. Tal Rabin, awarded this morning the Award for Excellence in Mathematics, claimed it would cost $250,000 to 51% attack Bitcoin for 1 hour. Tal Rabin, your math is wrong! That number is actually on the order of 1000 times too small.