You are given a string very likely that it's base64 of some data (its length is divisible by 4 and last character is '=' sign). So:$ base64 --decode > fileQlpoOTFBWSZTWTxSmOAAAAsJAF/gOwAgADEAAAiZMNT0JbKzhCQcyQtA2gNbvXgSvxdyRThQkDxS<span>mOA=$ cat fileBZh91AY..(binary file)Google BZh91AY, find bz2$ bzip2 -d filebzip2: Can't guess original name for file -- using file.out$ cat file.out9afa828748387b6ac0a393c00e542079The key is: </span>9afa828748387b6ac0a393c00e542079