Home ›

Distributed Hash Tables, Part I

Issue 114

From Issue #114
October 2003

Oct 01, 2003  By Brandon Wiley
 in
Distributed hash tables are an essential component of robust peer-to-peer networks. Learn to write applications that let everyone's copy share the same data.

Listing 6. portscan.py

def __main__():
    id=int(random.uniform(0,2**k))
    node=Node(id)
    join(node, initialContact)

    line=raw_input('Enter an IP to scan: ').trim()
    key=long(sha.new(line).hexdigest(),16)
    value=lookup(node, key)
    if value==None:
        f=os.popen('nmap '+args[1])
        lines=f.readlines()
        value=string.join(lines, '\n')
        store(node, key, value)

In this installment of our two-part series, we discussed the theory behind building DHTs. Next time, we'll talk about practical issues in using DHTs in real-world applications.

Resources

Achord: thalassocracy.org/achord/achord-iptps.html

Chord: www.pdos.lcs.mit.edu/chord

Curious Yellow: blanu.net/curious_yellow.html

How Can You Defend against a Superworm? linuxjournal.com/article/6069

Kademlia: kademlia.scs.cs.nyu.edu

Brandon Wiley is a peer-to-peer hacker and current president of the Foundation for Decentralization Research, a nonprofit corporation empowering people through technology. He can be contacted at blanu@decentralize.org.

______________________

Comments

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Wrong Algorithm

Bob-PT's picture
Submitted by Bob-PT (not verified) on Sun, 05/03/2009 - 03:17.

the last else in distance should return (2**k)-(b-a), otherwise id would exceed the longest possible distance, i.e. the ring size.
Btw, nice article ;)

Re: Wrong Algorithm

DougC's picture
Submitted by DougC (not verified) on Tue, 09/08/2009 - 15:09.

After the last else in the distance function, b < a, so (b-a) is negative. The sum of (2**k) and (b-a) will still be less than (2**k).

Wrong Algorithm

Anonymous's picture
Submitted by Anonymous (not verified) on Thu, 08/24/2006 - 11:36.

The findNode should return current.next

White Paper
More Resources
Fabric-Based Computing Enables Optimized Hyperscale Data Centers

Today’s modular x86 servers are compute-centric, designed as a least common denominator to support a wide range of IT workloads. Those generic, virtualized IT workloads have much different resource optimization requirements than hyperscale and cloud applications. They have resulted in a “one size fits all” enterprise IT architecture that is not optimized for a specific set of IT workloads, and especially not emerging hyperscale workloads, such as web applications, big data, and object storage. In this report, you will learn how shifting the focus from traditional compute-centric IT architectures to an innovative disaggregated fabric-based architecture can optimize and scale your data center.

Learn More

Sponsored by AMD

White Paper
More Resources
Red Hat White Paper: Using an Open Source Framework to Catch the Bad Guy

Built-in forensics, incident response, and security with Red Hat Enterprise Linux 6

Every security policy provides guidance and requirements for ensuring adequate protection of information and data, as well as high-level technical and administrative security requirements for a system in a given environment. Traditionally, providing security for a system focuses on the confidentiality of the information on it. However, protecting the data integrity and system and data availability is just as important. For example, when processing United States intelligence information, there are three attributes that require protection: confidentiality, integrity, and availability.

Learn more about catching the bad guy in this free white paper.

Learn More

Sponsored by DLT Solutions