Micro-Bitcoin

C++ Bitcoin library for microcontrollers. Supports Arduino, ARM mbed, bare metal.
It provides a collection of convenient classes for Bitcoin and general elliptic curve ariphmetics.
This library is built on top of trezor-crypto library. API is inspired by Jimmy's Porgramming Blockchain class and book.

Documentation: https://micro-bitcoin.github.io/docs/.

Classes and functions

Key management:

Classes:

• PrivateKey - a single private key class. Stores the 32-byte secret and network information (mainnet or testnet). Can be exported / imported as WIF. Inherits functionality from ECScalar - you can add, multiply, divide them, multiply PublicKey by it etc.
• PublicKey - a single public key class. Inherits functionality from ECPoint class - you can add them, multiply by scalar etc.
• HDPrivateKey - HD wallet private key with bip32 functionality. For common derivation pathes (bip44/49/84) automatically detects the script types. Can derive children and hardened children, can be derived from mnemonic or seed.
• HDPublicKey - An HD public key corresponding to a particular HD private key. Can derive children, but not hardened.

Handy functions:

• generateMnemonic(int strength) - generates a new mnemonic using RNG
• generateMnemonic(const uint8_t * entropy_data, size_t length) - generates mnemonic from byte array
• generateMnemonic(const char * entropy_string) - generates mnemonic from the string

Other Bitcoin classes

• Signature - ECDSA signature
• Script
• Witness
• Tx - transaction class
• TxIn
• TxOut

Extra classes:

• PSBT - partially signed bitcoin transaction (bip174)
• ElectrumTx - unsigned electrum transaction, poorly implemented, consider using PSBT instead.

Elliptic curve math

• ECScalar - a 256-bit number modulo N (curve order)
• ECPoint - a point on an elliptic curve (secp256k1)

Hash functions

Hash functions defined in Hash.h file.

Single line functions:

• sha256
• sha256Hmac
• sha512
• sha512Hmac
• rmd160
• hash160 - rmd160(sha256(m))
• doubleSha

And corresponding hash classes (with HMAC support):

• SHA256
• SHA512
• RMD160
• Hash160
• DoubleSha

Future development

Roadmap:

• external key storage support (i.e. smart cards and chips like ATECC608A)
• cryptoaccelerators and TRNG support
• handy functions to construct knowns script - HTLC, multisig, timelocks
• script evaluation
• tests (especially on the edge cases)
• security audit of the code - improve on sidechannels etc
• micro-python bindings
• lightning support (probably gonna be a separate library)
• memory optimizations (internal storage for large transactions to reduce RAM footprint etc)

Classes to be implemented:

• BlockHeader
• MerkleProof