code: public void reset() {
          super.reset();
  
          /* SHA-256 initial hash value
           * The first 32 bits of the fractional parts of the square roots
           * of the first eight prime numbers
           */
  
          H1 = 0x6a09e667;
          H2 = 0xbb67ae85;
          H3 = 0x3c6ef372;
          H4 = 0xa54ff53a;
          H5 = 0x510e527f;
          H6 = 0x9b05688c;
          H7 = 0x1f83d9ab;
          H8 = 0x5be0cd19;
  
          xOff = 0;
          for (int i = 0; i != X.length; i++) {
              X[i] = 0;
          }
      }
docs: reset the chaining variables