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BIP32: edits by ddustin for clarity #1903

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BIP32: edits by ddustin for clarity #1903

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7 changes: 5 additions & 2 deletions bip-0032.mediawiki
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Expand Up @@ -52,10 +52,11 @@ Addition (+) of two coordinate pair is defined as application of the EC group op
Concatenation (||) is the operation of appending one byte sequence onto another.

As standard conversion functions, we assume:
* point(p): returns the coordinate pair resulting from EC point multiplication (repeated application of the EC group operation) of the secp256k1 base point with the integer p.
* point(p): returns the coordinate pair resulting from EC point multiplication (repeated application of the EC group operation) of the secp256k1 base point with the integer p (similar to making a public key).
* ser<sub>32</sub>(i): serialize a 32-bit unsigned integer i as a 4-byte sequence, most significant byte first.
* ser<sub>256</sub>(p): serializes the integer p as a 32-byte sequence, most significant byte first.
* ser<sub>P</sub>(P): serializes the coordinate pair P = (x,y) as a byte sequence using SEC1's compressed form: (0x02 or 0x03) || ser<sub>256</sub>(x), where the header byte depends on the parity of the omitted y coordinate.
* ser<sub>P</sub>(P): serializes the coordinate pair P = (x,y) (i.e., the public key) as a byte sequence using [https://github.com/bitcoin-core/secp256k1/blob/b9313c6e/include/secp256k1.h#L227 SEC1]'s compressed form: (0x02 or 0x03) || ser<sub>256</sub>(x), where the header byte depends on the parity of the omitted y coordinate.
** [https://github.com/bitcoin-core/secp256k1 Libsecp256k1]'s pubkey_serialize and pubkey_parse functions implement this format.
* parse<sub>256</sub>(p): interprets a 32-byte sequence as a 256-bit number, most significant byte first.


Expand All @@ -65,6 +66,8 @@ In what follows, we will define a function that derives a number of child keys f

We represent an extended private key as (k, c), with k the normal private key, and c the chain code. An extended public key is represented as (K, c), with K = point(k) and c the chain code.

When deriving child keys, a "hardened" child key can only be generated using a private key. This provides security advantages and prevents adversarial public key tracing.

Each extended key has 2<sup>31</sup> normal child keys, and 2<sup>31</sup> hardened child keys. Each of these child keys has an index. The normal child keys use indices 0 through 2<sup>31</sup>-1. The hardened child keys use indices 2<sup>31</sup> through 2<sup>32</sup>-1. To ease notation for hardened key indices, a number i<sub>H</sub> represents i+2<sup>31</sup>.

===Child key derivation (CKD) functions===
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