Question

For my iPhone application, Apple wants to know if my password encryption (md5) is greater then 64-bit symmetric or greater then 1024-bit symmetric. I have not been able to find it online, so I am wondering if anyone knows the answer. In addition, is this considered an appropriate encryption technology for passwords, or should I use something different?

Thanks for any help!

Answer 1

MD5 is a hashing function, thus by definition it is not reversible. This is not the case for encryption (either symmetric or asymmetric), which has to be reversible to be useful.

To be more precise, hashes are one-way functions, in that an infinite number of inputs can map to a single output, thus it is impossible to obtain the exact input, with certainty, that resulted in a given output.

However, it may be possible to find a different input that hashes to the same output. This is called a collision.

Generally, hashing passwords instead of storing the plain text (even encrypted) is a good idea. (Even better if using a salt) However, MD5 has known weaknesses (and large collections of rainbow tables that aid in finding collisions), thus it would be a good idea to switch to something like SHA-1 or one of the SHA-2 family of hashes.

However, to answer your original question, there is really is no way to compare MD5 or any hash against any type of encryption; they have no equivalents because it’s like comparing apples and oranges.