"Who knows for certain?
Who shall here declare it?
Whence was it born, whence came creation?
No one knows whence creation arose;
and whether God has or has not made it.
He who surveys it from the lofty skies, only he knows--or perhaps he knows not.--- RIG VEDA
" It's because for passwords the admin doesn't need to know the password , but for things where you need to retrieve the data, it has to be a two way encryption.
Actually there is no reason AT ALL to make passwords retrieveable, as admins(creator/creators creator) will have the permissions necessary to reset passwords should the need arise. So to answer your question, password applications are one place where one way encryption is used.
It is also used (or can be) in high security applications where the need to protect the data encrypted outweighs the need to access the data should passwords be forgotten.
Let's say a password is encrypted one-way. That way there is no way to get it back, but if you encrypt the same password, you'll get the same result (most likely a really long string of 0-F characters).
When someone tries to use that password to log in, it encrypts it the same way as the master password. If the two encrypted strings match, the login is successful.
Basically, it's impossible to unencrypt the master password, but you can encrypt another string and see if it matches the original."
Are we alone in this Universe? is a definite NO . may be there might be some other replication/comparison model life farms existing in another part of the universe used for the same purpose.