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Keywords: C++, Open SSL, Hash functions

📝 Task Objective:

Your task is to implement a function (or a set of functions, not a full program) that finds any message whose hash (SHA-512) starts with a specified sequence of zero bits from the left. The bit order is big-endian: Byte 0 from MSB to LSB, Byte 1 from MSB to LSB, ..., last byte from MSB to LSB. In other words, two zero bits correspond to a byte like 0010 0111 (0x27).

The function is required in two variants:

  1. Basic solution (findHash function). The implementation of this function is mandatory.
  2. Enhanced solution (findHashEx function). The implementation of this function is optional, but a dummy implementation must be provided to compile the task. Implement this function if you aim for a bonus.

📥 Function Parameters:

int findHash(int bits, string &message, string &hash)
  • bits: The required number of zero bits in the hash of the message.
  • message: Output parameter. This parameter will contain the data for which the corresponding hash was found. The result is stored as a hexadecimal string.
  • hash: Output parameter. This is the hash of the message from the previous parameter, also stored as a hexadecimal string.
  • Return value: The function returns 1 on success, 0 on failure or invalid parameters (typically, an unreasonable number of zero bits).
int findHashEx(int bits, string &message, string &hash, string_view hashFunction)
  • Extension of findHash: All parameters and return value remain the same as in the basic variant.
  • hashFunction: A new parameter that specifies which hash function should be used to find the sequence of zero bits. The provided hash function name must be compatible with EVP_get_digestbyname.