DIY Bitcoin Hardware
/
secp256k1_example
Simple example of secp256k1 library
main.cpp
- Committer:
- diybitcoinhardware
- Date:
- 2019-09-16
- Revision:
- 2:6b892a0b43e5
- Parent:
- 0:23d71aa111c7
File content as of revision 2:6b892a0b43e5:
#include "mbed.h" #include "secp256k1.h" #include "secp256k1_preallocated.h" RawSerial pc(SERIAL_TX, SERIAL_RX, 115200); // small helper functions that prints // data in hex to the serial port void print_hex(const uint8_t * data, size_t data_len){ for(int i=0; i<data_len; i++){ printf("%02x", data[i]); } } // just adds a new line to the end of the data void println_hex(const uint8_t * data, size_t data_len){ print_hex(data, data_len); printf("\r\n"); } // prints error and hangs forever void err(const char * message, void * data = NULL){ printf("ERROR: %s\r\n", message); while(1){ wait(1); } } void secp_example(){ // secp256k1 context secp256k1_context *ctx = NULL; int res; // to store results of function calls size_t len; // to store serialization lengths printf("=== secp256k1 context ===\r\n"); // first we need to create the context // this is the size of memory to be allocated size_t context_size = secp256k1_context_preallocated_size(SECP256K1_CONTEXT_VERIFY | SECP256K1_CONTEXT_SIGN); printf("Context size: %u bytes\r\n", context_size); // creating the context ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY | SECP256K1_CONTEXT_SIGN); printf("Context created\r\n"); printf("=== Secret key ===\r\n"); // some random secret key uint8_t secret[] = { 0xbd, 0xb5, 0x1a, 0x16, 0xeb, 0x64, 0x60, 0xec, 0x16, 0xf8, 0x4d, 0x7b, 0x6f, 0x19, 0xe2, 0x0d, 0x9b, 0x9a, 0xb5, 0x58, 0xfa, 0x0e, 0x9a, 0xe4, 0xbb, 0x49, 0x3e, 0xf7, 0x79, 0xf1, 0x40, 0x55 }; printf("Secret key: "); println_hex(secret, sizeof(secret)); // Makes sense to check if secret key is valid. // It will be ok in most cases, only if secret > N it will be invalid res = secp256k1_ec_seckey_verify(ctx, secret); if(!res){ err("Secret key is invalid"); } /**************** Public key ******************/ printf("=== Public key ===\r\n"); // computing corresponding pubkey secp256k1_pubkey pubkey; res = secp256k1_ec_pubkey_create(ctx, &pubkey, secret); if(!res){ err("Pubkey computation failed"); } // serialize the pubkey in compressed format uint8_t pub[33]; len = sizeof(pub); secp256k1_ec_pubkey_serialize(ctx, pub, &len, &pubkey, SECP256K1_EC_COMPRESSED); printf("Public key: "); println_hex(pub, len); // this is how you parse the pubkey res = secp256k1_ec_pubkey_parse(ctx, &pubkey, pub, 33); if(res){ printf("Key is valid\r\n"); }else{ printf("Invalid key\r\n"); } /**************** Signature stuff ******************/ printf("=== Signature generation ===\r\n"); // hash of the string "hello" uint8_t hash[32] = { 0x2c, 0xf2, 0x4d, 0xba, 0x5f, 0xb0, 0xa3, 0x0e, 0x26, 0xe8, 0x3b, 0x2a, 0xc5, 0xb9, 0xe2, 0x9e, 0x1b, 0x16, 0x1e, 0x5c, 0x1f, 0xa7, 0x42, 0x5e, 0x73, 0x04, 0x33, 0x62, 0x93, 0x8b, 0x98, 0x24 }; // signing secp256k1_ecdsa_signature sig; res = secp256k1_ecdsa_sign(ctx, &sig, hash, secret, NULL, NULL); if(!res){ err("Can't sign"); } // serialization uint8_t der[72]; len = sizeof(der); res = secp256k1_ecdsa_signature_serialize_der(ctx, der, &len, &sig); if(!res){ err("Can't serialize the signature"); } printf("Signature: "); println_hex(der, len); // verification printf("=== Signature verification ===\r\n"); res = secp256k1_ecdsa_verify(ctx, &sig, hash, &pubkey); if(res){ printf("Signature is valid\r\n"); }else{ printf("Invalid signature\r\n"); } secp256k1_context_destroy(ctx); } int main(){ printf("Press any key to continue\r\n"); pc.getc(); printf("Ready to go!\r\n"); printf("=== Running example for secp256k1 ===\r\n"); secp_example(); printf("\r\n=== Done ===\r\n"); }