This question already has an answer here:
Both bcrypt and scrypt hashing algorithms are designed to increase the resources required during the computation. Hashing passwords with these algorithms can be beneficial as it makes the task of an offline attacker more difficult.
The time required to hash a password can be increased by increasing the number of iterations in bcrypt. The attacker then has to execute this iterations in sequential manner as there is no assumed shortcut.
The memory required to hash a password can be increased in scrypt. The attacker will therefore need a large amount of memory to mount parallel attacks.
As, I understand both these algorithm attempt to thwart the parallel attacks.
My question is can we make SHA-x or any exiting secure hash algorithm iterative and memory intensive, and achieve the same functionality as that of bcrypt and scrypt?