2 SFC / CSO [email protected] — 2 — 2017-02-08 – p.1/48 

Proof of Work API — 2 — 2017-02-08 – p.2/48 

1. 2. 3. 4. - 5. - 6. — 2 — 2017-02-08 – p.3/48 

1. — 2 — 2017-02-08 – p.4/48 

vs. ( ) http://www.post.japanpost.jp/service/letax/index.html https://e-naiyo.post.japanpost.jp/ ( ⇒ ) ( ) — 2 — 2017-02-08 – p.5/48 

Satoshi Nakamoto, “Bitcoin: A Peer-to-Peer Electronic Cash System”, 2008 P2P http://bitcoin.org/ BTC (ISO XBT ) 2013 11 1BTC 10 — 2 — 2017-02-08 – p.6/48 

2. — 2 — 2017-02-08 – p.7/48 

(1) 2,100 cm3 1 1cm3 10 12.5cm3 ⇒ — 2 — 2017-02-08 – p.8/48 

(2) ( ) ( ) ( ) ( ) → — 2 — 2017-02-08 – p.9/48 

= or : → — 2 — 2017-02-08 – p.10/48 

3. — 2 — 2017-02-08 – p.11/48 

- — 2 — 2017-02-08 – p.12/48 

- RSA, DSA, ECDSA ( DSA) ( RSA) PKI — 2 — 2017-02-08 – p.13/48 

4. - — 2 — 2017-02-08 – p.14/48 

— 2 — 2017-02-08 – p.15/48 

(1) (= ) → — 2 — 2017-02-08 – p.16/48 

(2) M A 60BTC (SegWit . . . ) — 2 — 2017-02-08 – p.17/48 

— 2 — 2017-02-08 – p.18/48 

1. 10 ( ) 2. 3. 1 — 2 — 2017-02-08 – p.19/48 

End-to-End ( ) ( ) — 2 — 2017-02-08 – p.20/48 

— 2 — 2017-02-08 – p.21/48 

21 ( 4 ) ( ) 2,100 BTC 1 1 BTC 2140 20,999,999.9769 BTC — 2 — 2017-02-08 – p.22/48 

— 2 — 2017-02-08 – p.23/48 

CPU → GPU → FPGA → ASIC ( ) → → — 2 — 2017-02-08 – p.24/48 

— 2 — 2017-02-08 – p.25/48 

POW ( ) Proof Of Work . . . — 2 — 2017-02-08 – p.26/48 

(2014 2 ∼2016 1 ) — 2 — 2017-02-08 – p.27/48 

( ) — 2 — 2017-02-08 – p.28/48 

5. - — 2 — 2017-02-08 – p.29/48 

Transaction Data Structure Field Description Size (bytes) Version Currently 1 4 # of inputs Positive var-int 1∼9 List of inputs Variable # of outputs Positive var-int 1∼9 List of outputs Variable Lock time 4 Lock time is used for micropayment channels, for example — 2 — 2017-02-08 – p.30/48 

Output Data Structure Field Description Size (bytes) Amount Value in 10−8BTC 8 Script length Positive var-int 1∼9 Script Variable — 2 — 2017-02-08 – p.31/48 

Input Data Structure Field Description Size (bytes) Referred TX Double SHA-256 value 32 Referred output Index of the output 4 Script length Positive var-int 1∼9 Script Variable Sequence # 4 — 2 — 2017-02-08 – p.32/48 

Major Script Operators Operator Code Description OP_0 0 Push 0 byte N/A 1∼0x4b Push # bytes OP_PUSHDATA1 0x4c Push length specified by 1-byte suffix OP_PUSHDATA2 0x4d Push length specified by 2-byte suffix OP_PUSHDATA4 0x4e Push length specified by 4-byte suffix OP_NOP 0x61 Do nothing OP_VERIFY 0x69 TX invalid if not true OP_RETURN 0x6a Fail immediately (unspendable) OP_DUP 0x76 Copy 1 item OP_EQUAL 0x87 If 2 items match OP_EQUALVERIFY 0x88 OP_EQUAL → OP_VERIFY OP_HASH160 0xa9 Apply SHA-256→RIPEMD-160 OP_CHECKSIG 0xac If signature for TX verified OP_CHECKMULTISIG 0xae If multiple signatures for TX verified Script is a stack-oriented language with postfix notation — 2 — 2017-02-08 – p.33/48 

Script (General) Output: OP_DUP OP_HASH160 OP_PUSHDATA* OP_EQUALVERIFY OP_CHECKSIG Input: OP_PUSHDATA* OP_PUSHDATA* TX output addressed to a public-key digest and referring input — 2 — 2017-02-08 – p.34/48 

Script Processing Concatinates scripts: input → output Stack-based processing — 2 — 2017-02-08 – p.35/48 

Script (Generation) Output: OP_PUSHDATA* OP_CHECKSIG Input: OP_PUSHDATA* Gen. TX otuput and referring input No need to specify public key by its digest Can avoid compromising security down to 160bit — 2 — 2017-02-08 – p.36/48 

Block Data Structure Field Description Size (bytes) Block header 6 items 80 # of TXs Positive var-int 1∼9 List of TXs Variable — 2 — 2017-02-08 – p.37/48 

Block Header Data Structure Field Description Size (bytes) Version 4 Digest Double SHA-256 value 32 Merkle root Double SHA-256 value 32 Time Seconds (since 1970-01-01T00:00 UTC) 4 Target Compressed format 4 Nonce Appropriate value 4 Merkle root is the digest of all TXs — 2 — 2017-02-08 – p.38/48 

Merkle Tree Digest = double SHA-256 value Existence of a TX can be verified if a relevant subtree is provided — 2 — 2017-02-08 – p.39/48 

Networking No structure All TCP, default port number: 8333 IPv6 supported since v0.7 of reference implementation (v0.13.2 as of Feb. 2017) Can use IPv4, IPv6 or Tor In reference implementation (as of v0.9) Max # of outbound connections : 8 Max # of all connections : 125 (by default) Only one outbound connection to an address group High 16bit in IPv4 High 32bit in IPv6 — 2 — 2017-02-08 – p.40/48 

Major Messages Category Name Function Connection version Sends version and block # verack Acknowledges version addr (address) Sends list of IP address/port # getaddr Requests addr Data inv (inventory) Sends (new) blocks and/or txs transfer getblocks Requests inv for all blocks within range getdata Requests block/tx by the digest block Sends block replying to getdata tx (transaction) Sends tx replying to getdata Header getheaders Requests headers for all blocks within range transfer headers Sends block headers up to 2,000 Others alert Broadcasts alert ping Confirms connection pong Acknowledges ping — 2 — 2017-02-08 – p.41/48 

Message Structure Field Description Size (bytes) Magic number 0xd9b4bef9 4 Command Message name (ASCII string) 12 Payload length Size of payload in bytes 4 Checksum Double SHA-256 value of payload First 4 Payload Message data Variable All integers are encoded in Little Endian except IP address and port # We’ve just seen the payloads for block and tx messages — 2 — 2017-02-08 – p.42/48 

DNS Seed seed.bitcoin.sipa.be dnsseed.bluematt.me dnsseed.bitcoin.dashjr.org seed.bitcoinstats.com seed.bitnodes.io bitseed.xf2.org Maintained by volunteers None of these uses DNSSEC (as of v0.10) — 2 — 2017-02-08 – p.43/48 

Transfer Protocol block message is handled in the same manner — 2 — 2017-02-08 – p.44/48 

For more detail, see https://bitcoin.org/en/developer-reference — 2 — 2017-02-08 – p.45/48 

6. — 2 — 2017-02-08 – p.46/48 

BTC ( ) LTC ( ) DOGE ( ) ETH ( ) — 2 — 2017-02-08 – p.47/48 

— 2 — 2017-02-08 – p.48/48