Bitmessage:An

Analysis

Vikram Reddy Pareddy

CSc 8222

Department of Computer Science, Georgia State University

Email

• SMTP – 1981

• Simple Protocol - designed mainly for academic

and government use.

• No data protection strategies included

SMTP

Improvements on SMTP

• Sender Policy Framework(SPF) – It is an email

validation system that tries to prevent spam by

detecting spoofing, by verifying sender’s IP

address. The domain administrators are expected

to designate hosts in that domain that are

legitimate hosts.

• Domain Keys Identified Mail(DKIM) – It is a

method of associating a domain name to the

email message to make someone responsible for

the email. This responsibility is set by using digital

signatures.

Secure Email

• PGP – 1991 – Phil Zimmerman

• It uses signing, encryption, certificates etc. to

create secure environments – for email or for

encrypted file systems etc.

• Public key authentication – decentralized

• Web of Trust

Web of Trust

Assumptions in Web of Trust

• In order to verify the key, the assumption made is

that everyone signs the key of others

• Also everyone submits these signatures to the key

servers.

Idea of PGP

Off the record messaging

• Cryptographic protocol used to provide strong

encryption for instant messaging and email

• It uses a combination of AES symmetric key

encryption, Diffie-Hellman key exchange, and

SHA-1 hash function.

Advantages of OTR systems

• Encryption

• Authentication

• Deniable Encryption

• Perfect Forward Secrecy

Invisible Internet Project

• Provides a layer that serves secure

communication/data transfer mechanism

• Introduced in 2003 as a beta software

• Not reviewed yet

• No anonymity guaranteed

Issues with protocols based

on SMTP

Bitcoin

• Open source decentralized Peer to Peer currency

• No central authority

• Not designed for anonymity

• Proof of work

• Mining

Bitmessage

• Based on Bitcoin, although it is designed to

handle a different application

• It differs from the protocols based on SMTP as it is

based on the concept of EGE or “Everyone Gets

Everything”

• Using this concept, Bitmessage can not only mask

the message body but also the metadata

associated with the message i.e. the sender and

receiver

EGE

• No end points to a message

• Encrypt the message and drop it into the block

chain of messages

• All the active users try to decrypt the message.

• Only the intended recipient will be able to decrypt

the message.

Other services of Bitmessage

Broadcasting

• Since Bitmessage is based on the concept of

EGE, broadcasting a message comes naturally

• The users have to get the password of the

channel from some forum or word of mouth – and

then they will be able to decrypt the messages

using the password

Chans

• Chans or channels are anonymous chat rooms

• Users can simply encrypt using the public key of

the chat room and post it

• Completely anonymous

Perfect Forward Secrecy

• An intruder can store all the encrypted

conversations and later when he eventually

breaks or somehow gets the private key, all the

previously encrypted information is lost

• This is a concern in almost all the PKI systems

• In Bitmessage this concern is even more

pronounced as anyone can store the block chains

easily

• Bitmessage doesn’t provide PFS

• However, this can be supported in Bitmessage

using and implementation of key rotation

• Every message that is sent has to be sent using a

new key. These are called ephemeral keys

Message Retention

• In Bitmessage, the messages are retained for two days before they are deleted

• The sender expects an acknowledgement from the receiver which confirms the delivery of the message

• If the receiver doesn’t check his mailbox in two days that the message was sent, the messae is lost and the sender has to send it again

This concept is being improved using the Time-to-live concept

Streams

• According to Prof. Tom Rodden of Univ of Nottingham, 2.8 million mails are being sent per second across the world.

• If Bitmessage is expected to store all these messages, it has to implement some concept compared to the normal block chain used by bitcoin

• For this, Bitmessage uses Streams.

• Streams are a way to self-segregate the messages when the volume of the messages is too high

• When the volume of messages become too high,

the client can divide the block chain into child

streams

• Problem: Inter stream messaging is not possible

in Bitmessage.

• If the receiver of the message is in a different

stream, the sender has to create an address in

that other stream in order to send the message.

Conclusion

• Bitmessage completely redesigns the email

system

• It is completely anonymous

• There are a few issues that still exist such as

Perfect Forward Secrecy and the question of

scalability

Future Work

• An MIT graduate has developed a new protocol

based on Bitmessage

• This message is called Bitmask or Bitmessage

2.0. This protocol uses bandwidth based metrics

instead of proof of work

• A protocol called LibertyMail is being developed

which is again based on Bitmessage system

Idea

• Currently, Bitmessage, like bitcoin in the beginning has only one client, Bitmessage-Qt

• This is a standalone client in the system which is used independent of any mail client

• The problem with this kind of client is that it downloads all the block chain into the individual system

• While this is a hindrance only when downloading the client for the first time, it is still a hindrance

• Bitcoin overcomes this hindrance by using a thin client based architecture

• Electrum is an example

• Electrum has its multiple servers located across the world.

• A person who wants to use a bitcoin client can generate the keys on his local machine and send it to the electrum server which posts it onto the block chain

• Electrum uses passphrase based electrum client

that creates deterministic addresses based on the

seed value.

• The idea of my project is to use a similar

architecture in Bitmessage.

• Using this architecture, we can still mask the

metadata