Abstract: A method and a system for implementing a reverse directory lookup using hash table, the method comprising: calculating using a hash function, a hash value of file name, upon creating a new file in a file system; writing the calculated hash value to the metadata of the file; reading the hash value at a meta data of a file of a desirable identifier (ID), responsive to an inquiry of a file name associated with the desirable ID; and searching for a corresponding file name for the desirable ID at a bucket storing all files associated with this bucket according to their filename's hash values, based on a hash function.