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Added support for "noise" over I1P/Tor to mask Tx transmission.

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Lee Clagett 2019-05-16 16:34:22 -04:00
parent bdfc63ae4d
commit 3b24b1d082
28 changed files with 2731 additions and 162 deletions
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52
ANONYMITY_NETWORKS.md
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@ -160,25 +160,6 @@ the system clock is noticeably off (and therefore more fingerprintable),
linking the public IPv4/IPv6 connections with the anonymity networks will be
more difficult.
### Bandwidth Usage
An ISP can passively monitor `monerod` connections from a node and observe when
a transaction is sent over a Tor/I2P connection via timing analysis + size of
data sent during that timeframe. I2P should provide better protection against
this attack - its connections are not circuit based. However, if a node is
only using I2P for broadcasting Monero transactions, the total aggregate of
I2P data would also leak information.
#### Mitigation
There is no current mitigation for the user right now. This attack is fairly
sophisticated, and likely requires support from the internet host of a Monero
user.
In the near future, "whitening" the amount of data sent over anonymity network
connections will be performed. An attempt will be made to make a transaction
broadcast indistinguishable from a peer timed sync command.
### Intermittent Monero Syncing
If a user only runs `monerod` to send a transaction then quit, this can also
@ -208,3 +189,36 @@ is a tradeoff in potential isses. Also, anyone attempting this strategy really
wants to uncover a user, it seems unlikely that this would be performed against
every Tor/I2P user.
### I2P/Tor Stream Used Twice
If a single I2P/Tor stream is used 2+ times for transmitting a transaction, the
operator of the hidden service can conclude that both transactions came from the
same source. If the subsequent transactions spend a change output from the
earlier transactions, this will also reveal the "real" spend in the ring
signature. This issue was (primarily) raised by @secparam on Twitter.
#### Mitigation
`monerod` currently selects two outgoing connections every 5 minutes for
transmitting transactions over I2P/Tor. Using outgoing connections prevents an
adversary from making many incoming connections to obtain information (this
technique was taken from Dandelion). Outgoing connections also do not have a
persistent public key identity - the creation of a new circuit will generate
a new public key identity. The lock time on a change address is ~20 minutes, so
`monerod` will have rotated its selected outgoing connections several times in
most cases. However, the number of outgoing connections is typically a small
fixed number, so there is a decent probability of re-use with the same public
key identity.
@secparam (twitter) recommended changing circuits (Tor) as an additional
precaution. This is likely not a good idea - forcibly requesting Tor to change
circuits is observable by the ISP. Instead, `monerod` should likely disconnect
from peers ocassionally. Tor will rotate circuits every ~10 minutes, so
establishing new connections will use a new public key identity and make it
more difficult for the hidden service to link information. This process will
have to be done carefully because closing/reconnecting connections can also
leak information to hidden services if done improperly.
At the current time, if users need to frequently make transactions, I2P/Tor
will improve privacy from ISPs and other common adversaries, but still have
some metadata leakages to unknown hidden service operators.