Skip to content

Latest commit

 

History

History

v0.2

README.md

(457) 0x02. Blockchain - Block mining

Specializations > System programming & Algorithm > Blockchain

Project author

Alexandre Gautier

Assignment dates

08-04-2021 to 08-06-2021

Description

Introduction to block mining, block difficulty, and proof of work.

Provided file(s)

provided/ (all originally here):

test/:

Mandatory Tasks

✅ 0. Proof of work

Write a function that checks whether a given hash matches a given difficulty

  • Prototype: int hash_matches_difficulty(uint8_t const hash[SHA256_DIGEST_LENGTH], uint32_t difficulty);, where:
    • hash is the hash to check
    • difficulty is the minimum difficulty the hash should match
  • Your function must return 1 if the difficulty is respected, or 0 otherwise
  • Refer to the concept page attached to this project to understand how the difficulty is represented in a hash

File(s): hash_matches_difficulty.c
Compiled: gcc -Wall -Wextra -Werror -pedantic -I. -I../../crypto -o hash_matches_difficulty-test hash_matches_difficulty.c test/hash_matches_difficulty-main.c -L../../crypto -lhblk_crypto -lllist -lssl -lcrypto -pthread

✅ 1. Block is valid v0.2

Modify the function int block_is_valid(block_t const *block, block_t const *prev_block); so that it checks that a block’s hash matches its difficulty

File(s): block_is_valid.c
Compiled: (from v0.1) gcc -Wall -Wextra -Werror -pedantic -I. -o block_is_valid-test blockchain_create.c block_create.c block_destroy.c blockchain_destroy.c block_hash.c block_is_valid.c test/block_is_valid-main.c -L../../crypto -lhblk_crypto -lllist -lssl -lcrypto -pthread

✅ 2. Block mining

Write a function that mines a block in order to insert it in the blockchain

  • Prototype: void block_mine(block_t *block);, where:
    • block points to the block to be mined
  • Your function must find a hash for block that matches its difficulty

File(s): block_mine.c
Compiled: gcc -Wall -Wextra -Werror -pedantic -I. -I../../crypto -o block_mine-test blockchain_create.c block_create.c block_destroy.c blockchain_destroy.c block_hash.c block_is_valid.c hash_matches_difficulty.c block_mine.c provided/_genesis.c provided/_blockchain_print.c test/block_mine-main.c -L../../crypto -lhblk_crypto -lllist -lssl -lcrypto -pthread

✅ 3. Adjust difficulty

Write a function that computes the difficulty to assign to a potential next block in the blockchain.

  • Prototype: uint32_t blockchain_difficulty(blockchain_t const *blockchain);, where:
    • blockchain points to the blockchain to analyze
  • Your function must return the difficulty to be assigned to a potential next block in the blockchain
  • The following macros must be defined in your header file blockchain.h
    • BLOCK_GENERATION_INTERVAL
      • Value: 1 (Will be changed during correction)
      • Defines how often (in seconds) a block should be found
    • DIFFICULTY_ADJUSTMENT_INTERVAL
      • Value: 5 (Will be changed during correction)
      • Defines how often (in blocks) the difficulty should be adjusted
  • If the latest block’s index is a multiple of DIFFICULTY_ADJUSTMENT_INTERVAL, AND that it is not the Genesis Block, the difficulty must be adjusted. Otherwise, the difficulty of the latest block in blockchain is returned
  • Difficulty adjustment:
    • Retrieve the last block for which an adjustment was made (the block with index <blockchain_size> - DIFFICULTY_ADJUSTMENT_INTERVAL)
    • Compute the expected elapsed time between the two Blocks
    • Compute the actual elapsed time
    • The difficulty must be incremented if the elapsed time is lower than half the expected elapsed time
    • The difficulty must be decremented if the elapsed time is greater than twice the expected elapsed time
    • The difficulty should not change otherwise

File(s): blockchain_difficulty.c
Compiled: gcc -Wall -Wextra -Werror -pedantic -I. -I../../crypto -o blockchain_difficulty-test blockchain_create.c block_create.c block_destroy.c blockchain_destroy.c block_hash.c blockchain_difficulty.c provided/_genesis.c provided/_blockchain_print.c test/blockchain_difficulty-main.c -L../../crypto -lhblk_crypto -lllist -lssl -lcrypto -pthread

Student