From 5757a02059909b02bc40c1e92b67b5bdbb915734 Mon Sep 17 00:00:00 2001 From: Shannon Appelcline Date: Tue, 11 Aug 2020 12:32:23 -1000 Subject: [PATCH] first half --- 16_3_Using_BIP32_in_Libwally.md | 131 +++++++++++++++++++++++++++++++- 1 file changed, 129 insertions(+), 2 deletions(-) diff --git a/16_3_Using_BIP32_in_Libwally.md b/16_3_Using_BIP32_in_Libwally.md index 77b906f..592ca63 100644 --- a/16_3_Using_BIP32_in_Libwally.md +++ b/16_3_Using_BIP32_in_Libwally.md @@ -1,6 +1,133 @@ -# 16.2: Using BIP32 in Libwally +# 16.3: Using BIP32 in Libwally > **NOTE:** This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning. -One of Libwally's greatest powers is that it can lay bare the underlying work of creating addresses. In particular, it supports [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki), which allows you to manipulate HD wallets, which are Hierarchical Deterministic Wallets, as described in [§3.5](03_5_Understanding_the_Descriptor.md). +In [§16.2](16_2_Using_BIP39_in_Libwally.md), you were able to use entropy to generate a seed and its related mnemonic. As you may recall from [§3.5: Understanding the Descriptor](03_5_Understanding_the_Descriptor.md), a seed is the basis of a Hierchical Deterministic (HD) Wallet, where that single seed can be used to generate many addresses. So how do you get from the seed to actual addresses? That's where [BIP32](https://en.bitcoin.it/wiki/BIP_0032) comes in. +## Creating HD Addresses + +To create a HD address requires starting with a seed, and then walking down the hierarchy until the point that you create addresses. + +That starts off easily enough, you just generate a seed, which you already did in the previous section: +``` + unsigned char entropy[16]; + randombytes_buf(entropy, 16); + + char *mnem = NULL; + lw_response = bip39_mnemonic_from_bytes(NULL,entropy,16,&mnem); + + unsigned char seed[BIP39_SEED_LEN_512]; + size_t seed_len; + lw_response = bip39_mnemonic_to_seed(mnem,NULL,seed,BIP39_SEED_LEN_512,&seed_len); +``` +### Generating a Root Key + +With a seed in hand, you can then generate a master extended key with the `bip32_key_from_seed_alloc` function (or alternatively the `bip32_key_from_seed`, which doesn't do the `alloc`): +``` + struct ext_key *key_root; + lw_response = bip32_key_from_seed_alloc(seed,sizeof(seed),BIP32_VER_TEST_PRIVATE,0,&key_root); +``` +As you can see, you'll need to tell it what version of the key to return, in this case `BIP32_VER_TEST_PRIVATE`, a private testnet key. + +> :link: **TESTNET vs MAINNET:** On mainnet, you'd instead ask for `BIP32_VER_TEST_PRIVATE`. + +### Generating xpub & xprv + +Whenever you have a key in hand, you can turn it into xpub or xprv keys for distribution with the `bip32_key_to_base58` command. You just tell it whether you want a `PRIVATE` (xprv) or `PUBLIC` (xpub) key: +``` + char *xprv; + lw_response = bip32_key_to_base58(key_root, BIP32_FLAG_KEY_PRIVATE, &xprv); + + char *xpub; + lw_response = bip32_key_to_base58(key_root, BIP32_FLAG_KEY_PUBLIC, &xpub); +``` + +### Understanding the Hierarchy + + /* 5. Generate key for account */ + + struct ext_key *key_account; + + uint32_t path_account[] = {BIP32_INITIAL_HARDENED_CHILD+84, BIP32_INITIAL_HARDENED_CHILD+1, BIP32_INITIAL_HARDENED_CHILD}; + + lw_response = bip32_key_from_parent_path_alloc(key_root,path_account,sizeof(path_account),BIP32_FLAG_KEY_PRIVATE,&key_account); + + if (lw_response) { + + printf("Error: bip32_key_from_parent_path_alloc failed: %d\n",lw_response); + exit(-1); + + } + + char *a_xprv; + lw_response = bip32_key_to_base58(key_account, BIP32_FLAG_KEY_PRIVATE, &a_xprv); + + if (lw_response) { + + printf("Error: account bip32_key_to_base58 failed: %d\n",lw_response); + exit(-1); + + } + + printf("Account xprv key: %s\r\n", a_xprv); + + char *a_xpub; + lw_response = bip32_key_to_base58(key_account, BIP32_FLAG_KEY_PUBLIC, &a_xpub); + + if (lw_response) { + + printf("Error: account bip32_key_to_base58 failed: %d\n",lw_response); + exit(-1); + + } + + printf("Account xpub key: %s\r\n", a_xpub); + + /* 6. Generate External Adress Key */ + + struct ext_key *key_external; + + lw_response = bip32_key_from_parent_alloc(key_account,0,BIP32_FLAG_KEY_PRIVATE,&key_external); + + if (lw_response) { + + printf("Error: root bip32_key_from_parent_alloc Level #1 failed: %d\n",lw_response); + exit(-1); + + } + + struct ext_key *key_address; + + lw_response = bip32_key_from_parent_alloc(key_external,0,BIP32_FLAG_KEY_PRIVATE,&key_address); + + if (lw_response) { + + printf("Error: root bip32_key_from_parent_alloc Level #2 failed: %d\n",lw_response); + exit(-1); + + } + + /* 7. Generate Address */ + + char *segwit; + lw_response = wally_bip32_key_to_addr_segwit(key_address,"tb",0,&segwit); + + printf("[84'/0'/0'/0/0]%s\n",segwit); + + /* Cleanup! */ + + bip32_key_free(key_address); + bip32_key_free(key_external); + bip32_key_free(key_account); + bip32_key_free(key_root); + + wally_free_string(xprv); + wally_free_string(xpub); + wally_free_string(a_xprv); + wally_free_string(a_xpub); + + wally_free_string(mnem); + + wally_cleanup(0); + +}