The traditional file system exists in a single computer, in order to search for other computer files, you must firstly know the computer's domain name or IP address, this will bring some problems:
a. Connection problem: first of all, it can not guarantee the fixed IP address of the machine online, the machine offline situation is common as a result of machine failure, unknown attacks or network reason;
b. Efficiency problem: if we all go to a website to download popular files, it will lead to the centralized file server transmission channel congestion, the download efficiency is low;
c. Security problem: It need provide the file server IP or domain name link address for sharing files, if the shared address disclosure, in fact, it provides a target for hackers to attack directly.
d. Trust problem: Once the machine has been hijacked by hackers , the contents of the file you get may be tampered, and it could be disastrous for using file.
PDFS（PeerSafe Distributed File System）is based on P2P Distributed Hash block file system, which connect the same file system of all computer equipment. It radically changes the user’s searching way. The user searches the content hash through PDFS. When the file is added to the PDFS node, it gets a new name. The name is actually an encrypted hash, which is calculated from the contents of the file. It uses encryption to ensure that the hash is always represented the content. Even if only one bit of data is modified in the file, the hash will be completely different.The files can be stored in different nodes, the more the file is accessed by other nodes, the more copies of the file. So the file can be extracted by some online nodes
When you ask hash to PDFS distributed network, by using a distributed hash table, it can quickly to find the node that owns the data and retrieve the data, then use the hash to verify whether it is the correct data.
PDFS is generic and free storage. The serve files can be large or small, to a few large file, it will automatically cut into small pieces, not only the PDFS nodes can download files from a server, but also to synchronized download from hundreds of servers. PDFS network is a fine-grained, unreliable, distributed, and easy to combine content distribution network (Delivery Network Content, CDN). Is very useful for all types of data, including images, video streams, distributed databases, operating systems, blockchains, etc.
PDFS does not need to store all of the released contents in the PDFS of each node. Instead, each node stores only what you want. If each node is hosting a little data, all data can be provided more space, bandwidth, and availability than any centralized network through the accumulation. Distributed network will soon become the world's fastest, most available, and the largest data storage. No one has the ability to close all the nodes, so the data will never be lost.
PeerSafe adopt the PDFS distributed file system protocol to develop the secure and reliable file sharing tool ShadowDisk, through the point to point communication way to construct distributed file system network, Address according to the contents of the file hash and extract the files, Protecting of the contents of the file not be tampered for free file sharing, and solved the problem of secure and efficient storage in distributed network.