Friends, please advise what jumps to set in the kangaroo code to find k nonce? I know that k nonce lies in the range n-2^40, n-1, but I don't understand what jumps to specify in the code so as not to miss the true k.
You can use algorithms like BSGS or Kangaroo, preferably Keyhunt (BSGS), to search for both possible coordinates simultaneously within the desired range. A 40-bit range is relatively small, and this would take less than 1 second.