This is the first part of a more technical talk where Andreas explores Bitcoin script, with examples from the 2nd edition of Mastering Bitcoin, focusing on the use of conditional statements, flow control, guard clauses and time locks. The examples will include advanced multi-signature scripts, hash time lock contracts and asymmetric revocable commitments. Then he answers questions about Bitcoin’s quirky bugs, where Bitcoin differs from Ethereum at a scripting level, how SegWit works, how consensus rules change, and whether Bitcoin is more than just a currency.

Watch Part 2 here:

This talk took place at the San Francisco Bitcoin Developer (@SFBitcoinDev) meetup on April 3rd, 2017:

Review materials on the topics presented:
Chpt. 7:
Chpt. 12:

The fundamentals of Bitcoin script 2:17
Bitcoin’s operators 5:00
Creating transactions (P2PKH – Pay to Public Key Hash) 6:30
Public Key CheckSigs, security by obfuscating public keys 7:42
Redeeming the script 9:05
The RIPEMD160 hash operation 12:05
OP_EQUALVERIFY, OP_CHECKSIG, & the elliptic curve digital signature algorithm (ECDSA) 14:05
Summary 18:30
Illustrating scripts: Equal, EqualVerify, CheckSig, CheckVerify, CheckMultisig, CheckLockTimeVerify 19:45
Guard clauses 23:02
Script-based timelocks 24:53
Flow control statements, interactive artificial intelligence 26:50
If, Else, EndIf 28:35
Unlocking scripts, what conditional flows do in Bitcoin 33:55
1-of-2 multi-signature script 35:44
1-of-2 multi-signature script with guard clause 38:28
2-of-3 multi-signature script 41:30
2-of-3 multi-signature script with timelock guard clause 43:20
BIP-113, how time is referenced in Bitcoin 44:42
Backup clause & other nuances in multi-signature schemes 46:58
Game theory, complexity from simplicity 52:36
2-of-3 multi-signature script, unlocking 53:45

Bitcoin: Where the Laws of Mathematics Prevail –
The rules of Bitcoin (part 1) –
The rules of Bitcoin (part 2) –
Forkology: A Study of Forks for Newbies –
Irreversibility and consumer protection –

Andreas M. Antonopoulos is a technologist and serial entrepreneur who has become one of the most well-known and well-respected figures in bitcoin.

Follow on Twitter: @aantonop

He is the author of two books: “Mastering Bitcoin,” published by O’Reilly Media and considered the best technical guide to bitcoin; “The Internet of Money,” a book about why bitcoin matters.




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Music: “Unbounded” by Orfan (
Outro Graphics: Phneep (
Outro Art: Rock Barcellos (