How many random elements before MD5 produces collisions?

Question

I\'ve got an image library on Amazon S3. For each image, I md5 the source URL on my server plus a timestamp to get a unique filename. Since S3 can\'t have subdirectories, I

Answer 1

A rough rule of thumb for collisions is the square-root of the range of values. Your MD5 sig is presumably 128 bits long, so you're going to be likely to see collisions above and beyond 2^64 images.