trezor-firmware/bip32.c

#include <string.h>

#include "bignum.h"
#include "hmac.h"
#include "ecdsa.h"
#include "bip32.h"

uint8_t hdnode_coin_version = 0x00;

void hdnode_from_pub(uint32_t version, uint32_t depth, uint32_t fingerprint, uint32_t child_num, uint8_t *chain_code, uint8_t *public_key, HDNode *out)
{
	out->version = version;
	out->depth = depth;
	out->fingerprint = fingerprint;
	out->child_num = child_num;
	memset(out->private_key, 0, 32);
	memcpy(out->chain_code, chain_code, 32);
	memcpy(out->public_key, public_key, 33);
	hdnode_fill_address(out);
}

void hdnode_from_seed(uint8_t *seed, int seed_len, HDNode *out)
{
	out->version = 0x0488ADE4; // main-net
	out->depth = 0;
	out->fingerprint = 0x00000000;
	out->child_num = 0;
	// this can be done because private_key[32] and chain_code[32]
	// form a continuous 64 byte block in the memory
	hmac_sha512((uint8_t *)"Bitcoin seed", 12, seed, seed_len, out->private_key);
	hdnode_fill_public_key(out);
	hdnode_fill_address(out);
}

int hdnode_private_ckd(HDNode *inout, uint32_t i)
{
	uint8_t data[1 + 32 + 4];
	uint8_t I[32 + 32];
	bignum256 a, b;

	if (i & 0x80000000) { // private derivation
		data[0] = 0;
		memcpy(data + 1, inout->private_key, 32);
	} else { // public derivation
		memcpy(data, inout->public_key, 33);
	}
	write_be(data + 33, i);

	bn_read_be(inout->private_key, &a);

	hmac_sha512(inout->chain_code, 32, data, sizeof(data), I);
	memcpy(inout->private_key, I, 32);
	memcpy(inout->chain_code, I + 32, 32);

	bn_read_be(inout->private_key, &b);
	bn_addmod(&a, &b, &order256k1);

	inout->depth++;
	inout->child_num = i;
	bn_write_be(&a, inout->private_key);

	hdnode_fill_public_key(inout);
	hdnode_fill_address(inout);
	return 1;
}

int hdnode_public_ckd(HDNode *inout, uint32_t i)
{
	uint8_t data[1 + 32 + 4];
	uint8_t I[32 + 32];
	curve_point a, b;
	bignum256 c;

	if (i & 0x80000000) { // private derivation
		return 0;
	} else { // public derivation
		memcpy(data, inout->public_key, 33);
	}
	write_be(data + 33, i);

	memset(inout->private_key, 0, 32);
	if (!ecdsa_read_pubkey(inout->public_key, &a)) {
		return 0;
	}

	hmac_sha512(inout->chain_code, 32, data, sizeof(data), I);
	memcpy(inout->chain_code, I + 32, 32);
	bn_read_be(I, &c);
	scalar_multiply(&c, &b); // b = c * G
	point_add(&a, &b);       // b = a + b
	inout->public_key[0] = 0x02 | (b.y.val[0] & 0x01);
	bn_write_be(&b.x, inout->public_key + 1);

	inout->depth++;
	inout->child_num = i;

	hdnode_fill_address(inout);
	return 1;
}

void hdnode_fill_public_key(HDNode *xprv)
{
	ecdsa_get_public_key33(xprv->private_key, xprv->public_key);
}

void hdnode_fill_address(HDNode *xprv)
{
	ecdsa_get_address(xprv->public_key, hdnode_coin_version, xprv->address);
}