> Most (all?) encryption functions are also hash functions, they're just special hash functions with the extra property of making it extremely difficult to discover the source.
The special property that encryption functions have compared to hashing functions isn't that it is extremely difficult to discover the source, but rather almost the reverse -- that for every encryption function there exists a function (decryption function) by which you can recover the unique source.
Hashing functions in general do not have an inverse function: while you might be able to recover several possible sources from them (and this might be easy or difficult), you cannot recover the single source, because the space of inputs is larger than the space of outputs, so there can be no unique mapping from outputs back to inputs that would generate them.
The special property that encryption functions have compared to hashing functions isn't that it is extremely difficult to discover the source, but rather almost the reverse -- that for every encryption function there exists a function (decryption function) by which you can recover the unique source.
Hashing functions in general do not have an inverse function: while you might be able to recover several possible sources from them (and this might be easy or difficult), you cannot recover the single source, because the space of inputs is larger than the space of outputs, so there can be no unique mapping from outputs back to inputs that would generate them.