I'm going to securely erase the data so I use shred which is a specialized the tool for this puprose. So I run shred -vfz /dev/sdd1 and it does its job:

shred: /dev/sdd1: pass 1/4 (random)...
shred: /dev/sdd1: pass 1/4 (random)...652MiB/932GiB 0%
shred: /dev/sdd1: pass 1/4 (random)...1,2GiB/932GiB 0%
shred: /dev/sdd1: pass 1/4 (random)...1,8GiB/932GiB 0%
shred: /dev/sdd1: pass 1/4 (random)...2,5GiB/932GiB 0%

However it is painfully slow. After an hour or so, it still could not finish the first pass on a 1TB HDD. So I'm wondering what is the quicker way to do so without compromizing the security of data removal?