Decrypt SHA1 Base64 Hash After spending a good hour searching I came across an article that explained that you can't reverse a hash value. How true is this? I need to reverse a base64 encoded Sha-1 email address but I can't seem to find a way without knowing what function was used to hash. Or is there an easier way of going about this?
You can very easily Base64-decode a string. 
SHA-1 was designed to prevent people from inverting it. It approximates a one-way function. 


See here for more. If it could be simply inverted, it would provide no information security. 

Your only feasible option is brute-force search.