I want to show a percentage indicator during a lengthy scrypt process. The simplest idea I can think of is this:
Pick N,r,p such that each crypto_scrypt() call is fast. Then repeat this same crypto_scrypt() call many times, passing the result of each crypto_scrypt() to the input (password) of the next crypto_scrypt(). The salt is kept the same for each call. The question is: Does this reduce security, as opposed to picking a larger p? In other words: Is picking p=1000 when calling crypto_scrypt() only once more secure than calling crypto_scrypt() with p=1 thousand times with the salt constant?
