Anonymity

Mail loops

A pseudonym may be configured to have replies sent through several remailer chains; this could be used to create loops that exponentially increase the load on a remailer Typically, the amount of mail a pseudonym can receive in a given day before being disabled is deliberately limited

(the) onion router (tor)

Alice (randomly) chooses her server path before sending. She sets up keys with each server along the path, and then encrypts the message in layers (LIKE AN ONION YA BIT) with each key. As the message is sent through the path, each server decrypts the next layer with its shared key. it's like a chain of proxy servers - each Tor connection goes through three (or more) nodes: the entry, middle node, and exit node To connect to Tor, the client first downloads a list of all Tor nodes from several directory authorities The nodes used for connections will be selected offline, so that no information about a client's route will be leaked

how to detect Tor

Assuming one can monitor a network link... If TLS encrypted data is sent to a Tor entry node, then one is likely using Tor Many gov't's (including the US) will pay "more" attention to you if it seems you are using Tor

should anonymity systems even be deployed?

Criminals, terrorists, etc. may use anonymity systems to avoid detection or prosecution Anonymity systems have been used for harassing people and by child predators But human rights groups, political dissidents, law enforcement agencies, etc. also use anonymity systems In some cases, anonymity systems could save lives

Tor hidden services

Each hidden service selects several middle nodes to act as "guards" (or introduction points) which are connected through additional Tor nodes to the hidden service Clients can look up guards for a hidden service in a distributed hash table Thus, the client has to route to the introduction point, and the introduction point will route to the hidden service

attacking remailers

Global eavesdropping Replay attacks Attacking specific remailers Spamming attacks Mail loops

Spamming attacks

If a pseudonym delivers messages to an email address, through a chain of remailers, the chain could be traced by an attacker who sends many "spam" messages to the pseudonym This can be thwarted by having messages delivered to a Usenet newsgroup or by limiting how many messages can be sent before the remailer chain is changed

is it ethical to use Tor?

If you are using for ethical means (privacy, for example), then yes Just because a technology can be used for illegal means does not automatically make that technology unethical If that were the case, then all of computers would be illegal

the benefits of using tor

It allows for "true" anonymity online It allows for much better privacy than otherwise is available The gov't cannot figure out what you are saying or doing (Although they can tell if you are using it)

Should attacks on anonymity systems be published?

Law enforcement agencies may be given an advantage with unpublished attacks Such attacks are likely to be discovered and kept secret by hostile governments, criminal hackers, etc.

the demise of Penet

Penet maintained a database mapping pseudonyms to email addresses - a single point of failure! Numerous requests for specific entries, and for the whole database, had been made while Penet was running The Church of Scientology just wanted to see them burn...

US government policy on Tor

Some agencies support it: US state department, NSF, and Radio Free Asia Some oppose it: NSA, FBI, CIA

anonymity theory "notions"

The adversary might be global - all the messages sent between nodes in the system might be observed The adversary might be able to take control of some of the nodes, both before and after observing messages (adaptive corruption) The adversary might send messages through the system, both before and after observing messages The adversary might be able to choose what messages are sent by honest parties

why people use Tor?

Tor is often used to defeat national firewalls; an ongoing area of work is disguising a Tor connection as a typical Firefox TLS connection A common pattern has emerged in such countries: Tor is typically blocked just before big announcements by the government, or immediately following news of rebellions or unrest in other countries

Given a tor path: Y (client) <-> A <-> B <-> C <-> S (server)

Y (client) <-> A <-> B <-> C <-> S (server) A is the entry relay or a bridge These are generally well known and published B and C are just relays Some are well known, others are kept secret As for S: If the destination is outside of Tor, then it sends the data (via TLS) to the destination, and S is called the exit relay If the destination is inside of Tor, then S is the hidden service

Fingerprinting

a local eavesdropper can collect information about latency patterns for specific systems accessed through Tor, and check for such patterns in a target connection This is particularly bad in cases where some information about a person's identity is leaked; for example, forum posts that use regional spellings or phrases

adaptive chosen ciphertext

allows the adversary to request decryptions of any ciphertext except the challenge, both before and after seeing the challenge

the Penet remailer

created in response to suggestions saying that people should be required to use their legal names online To use Penet, send an email requesting a pseudonym Mail sent to the pseudonym would be forwarded to the user's real email address A user could send an email to Penet, and have the message forwarded with their pseudonym in the "From:" field

why anonymity?

encryption is great for preventing people from reading your messages but it doesn't prevent people from seeing who you're corresponding with (which in some cases is more important than the content of the correspondence)

attacking tor

global eavesdropping Fingerprinting Malicious exit nodes

onion dildonics

i'm shook lmao apparently people are buying internet connected sex toys and then being pikachu when they're hacked like bruh

Malicious exit nodes

if end-to-end encryption is not used, a malicious exit can sniff usernames, passwords, and other information

Attacking specific remailers

if the adversary has some remailers under his control, he can flood other remailers in an attempt to prevent them from being used

receiving messages anonymously

is much easier than sending them anonymously Intelligence agencies have been taking advantage of this for decades, by broadcasting instructions to covert agents using shortwave radio, which has a global range We can duplicate this online: A message may be sent to a mailing list, posted to Usenet (e.g. in alt.anonymous.messages), uploaded to a blog or wiki, etc.

sender anonymity

is much more technically challenging than receiver anonymity

lessons learned from Penet

remailer control messages should be encrypted, so remailers can be chained (no single remailer should know both the sender and receiver of a message) Records should not be necessary for sending anonymous messages. To receive replies records need to be kept, but should allow for messages to be encrypted and forwarded through other remailers Those wishing to compromise remailers may be willing to go to great lengths, using legal or illegal means

replay attacks

sending the same message through a Remailer, and seeing what comes out This can be thwarted with maximum date headers, assuming PGP is non-malleable (which could be untrue), and does not work against Mixmaster remailers

provable security

showing that breaking a cryptosystem's security is at least as hard as solving a computationally difficult problem, such as the discrete logarithm problem

EIGamal

since EIGamal is based on the Diffie-Hellman key exchange, and we know that the discrete logarithm problem is computationally hard, then we can conclude that EIGamal is secure against any chosen plaintext attack

the drawbacks of having tor

this is how evil stuff is propogated online...

how the silk road was busted

two versions: "The FBI has claimed that the real IP address of the Silk Road server was found via data leaked directly from the site's CAPTCHA" Security researchers believe that the PHP login page was manipulated to output its server variables, including the IP address

cypherpunks remailers

using PGP to encrypt encrypt your email, then send to the remailer with a pseudoheader, and encrypt it using the remailer's public key they can be made more secure: re-encrypt part of the message using a symmetric cipher use random padding, or truncate below a certain line invalidate messages after a certain date, or after being remailed a certain number of times encrypt the subject line use a random number of remailer hops

global eavesdropping

watching all traffic through all remailers, and following one message This can be thwarted using random delays, random padding, and message reordering Tor does not have random delays or padding, so a global eavesdropper can defeat Tor