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Andrew Groot
54 lines
3.9 KiB
Markdown
54 lines
3.9 KiB
Markdown
# Address Types
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Addresses are commonly used identifiers that act as a shorthand for who can spend a given output.
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Since Bitcoin Cash [transactions](/protocol/blockchain/transaction) do not inherently have a concept of accounts with balances, it is not always easy (or even possible) to determine which unspent outputs are spendable by a given person.
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However, the [standard scripts](/protocol/blockchain/transaction/locking-script#standard-scripts) were designed to provide a straightforward structure that can be used to identify transactions that spendable in similar ways.
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In most cases, the address contains all of the information necessary to create a transaction output that is spendable by the owner of the address.
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Due to this and their compactness, addresses are the most common way to specify to others how ("where") they can receive funds.
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Raw addresses are rarely used outside of scripts, though, as they lack context and redundancy.
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Instead, addresses are typically encoded using the [Base58Check](/protocol/blockchain/encoding/base58check) or [CashAddr](/protocol/blockchain/encoding/cashaddr) formats to ensure they are received and interpreted correctly.
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These encodings include checksums as well as information about the type of address being encoded.
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CashAddr was created after Base58Check (also referred to as legacy encoding) to avoid conflicts with pre-existing BTC address.
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## Pay to Public Key Hash (P2PKH) Addresses
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[P2PKH](/protocol/blockchain/transaction/locking-script#pay-to-public-key-hash-p2pkh) addresses encode the hash of the public key that is locking the output (i.e. `RIPEMD-160(SHA-256(publicKey))`).
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Mainnet P2PKH addresses always start with `1` in Base58Check encoding and `q` in CashAddr encoding:
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Base58Check: 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa
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CashAddr: bitcoincash:qp3wjpa3tjlj042z2wv7hahsldgwhwy0rq9sywjpyy
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The following diagram show the full creation process for a P2PKH address:
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```mermaid
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graph LR
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PrivK["Private Key"] ==>PubK[Public key]
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PubK == SHA256 and RIPEMD160 ==> PubKH[Public Key Hash]
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PubKH ==> Address
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Address ==> PubKH
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style PubK fill:#F06,stroke:#333,stroke-width:2px;
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style PrivK fill:#B06,stroke:#333,stroke-width:8px;
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style PubKH fill:#0F6,stroke:#333,stroke-width:2px;
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style Address fill:#0F6,stroke:#333,stroke-width:2px;
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```
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## Pay to Script Hash (P2SH) Addresses
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[P2SH](/protocol/blockchain/transaction/locking-script#pay-to-script-hash-p2sh) addresses encode the redeem script hash (i.e. `RIPEMD-160(redeemScript)`).
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Mainnet P2SH addresses always start with `3` in Base58Check encoding and `p` in CashAddr encoding.
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Base58Check: 3N5i3Vs9UMyjYbBCFNQqU3ybSuDepX7oT3
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CashAddr: bitcoincash:pr0662zpd7vr936d83f64u629v886aan7c77r3j5v5
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## Multisig Addresses
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Multisig addresses are occasionally referenced despite there not being a specific process for creating them.
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This is because the addresses being referred to are actually P2SH addresses for redeem scripts that perform [multisignature](/protocol/blockchain/cryptography/multisignature) validation.
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As such, they look exactly like P2SH addresses and are indistinguishable from them until the script is known and inspected.
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Moreover, outputs created using multsig addresses use the P2SH script format, not the [Multisig (P2MS)](/protocol/blockchain/transaction/locking-script#multisig-p2ms) script format.
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Alternatively, with the advent of [Schnorr signatures](/protocol/blockchain/cryptography/signatures#schnorr-signatures) in BCH, it is also possible perform n-of-n multisignature locking and unlocking using [aggregated keys and signatures](/protocol/blockchain/cryptography/multisignature#private-multisignature).
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Only a single signature is produces, regardless of the number of parties involved, reducing the cost of multisignature validation and minimizing transaction size.
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This also means it could fit in a P2PKH (or P2PK) script, and therefore have a typical address of that type.
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This technique is newer, however, and not as widely implemented as the P2SH method. |