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==================
I2NP Specification
==================
.. meta::
:category: Protocols
:lastupdated: April 2020
:accuratefor: 0.9.46
.. contents::
Overview
========
The I2P Network Protocol (I2NP), which is sandwiched between I2CP and the
various I2P transport protocols, manages the routing and mixing of messages
between routers, as well as the selection of what transports to use when
communicating with a peer for which there are multiple common transports
supported.
.. _versions:
Protocol Versions
=================
All routers must publish their I2NP protocol version in the "router.version"
field in the RouterInfo properties. This version field indicates their level
of support for various I2NP protocol features, and is not necessarily the
actual router version.
If alternative (non-Java) routers wish to publish any version information about
the actual router implementation, they must do so in another property.
Versions other than those listed below are allowed. Support will be determined
through a numeric comparison; for example, 0.9.13 implies support for 0.9.12
features. Note that the "coreVersion" property is not used for determination
of the I2NP protocol version.
A basic summary of the I2NP protocol versions is as follows. For details, see
below.
============== ================================================================
Version Required I2NP Features
============== ================================================================
0.9.46 DatabaseLookup flag bit 4 for AEAD reply
0.9.44 X25519 keys in LeaseSet2
0.9.40 MetaLeaseSet may be sent in a DSM
0.9.39 EncryptedLeaseSet may be sent in a DSM
RedDSA_SHA512_Ed25519 signature type supported for
destinations and leasesets
0.9.38 DSM type bits 3-0 now contain the type;
LeaseSet2 may be sent in a DSM
0.9.36 NTCP2 transport support (if advertised in router address)
0.9.28 RSA sig types disallowed
0.9.18 DSM type bits 7-1 ignored
0.9.16 RI key certs / ECDSA and EdDSA sig types
Note: RSA sig types also supported as of this version, but
currently unused
DLM lookup types (DLM flag bits 3-2)
Minimum version compatible with vast majority of current network,
since routers are now using the EdDSA sig type.
0.9.15 Dest/LS key certs w/ EdDSA Ed25519 sig type (if floodfill)
0.9.12 Dest/LS key certs w/ ECDSA P-256, P-384, and P-521 sig types (if
floodfill)
Note: RSA sig types also supported as of this version, but
currently unused
Nonzero expiration allowed in RouterAddress
0.9.7 Encrypted DSM/DSRM replies supported (DLM flag bit 1) (if
floodfill)
0.9.6 Nonzero DLM flag bits 7-1 allowed
0.9.3 Requires zero expiration in RouterAddress
0.9 Supports up to 16 leases in a DSM LS store (6 previously)
0.7.12 VTBM and VTBRM message support
0.7.10 Floodfill supports encrypted DSM stores
0.7.9 or lower All messages and features not listed above
0.6.1.10 TBM and TBRM messages introduced
Minimum version compatible with current network
============== ================================================================
Note that there are also transport-related features and compatibility issues;
see the NTCP and SSU transport documentation for details.
.. _structures:
Common structures
=================
The following structures are elements of multiple I2NP messages.
They are not complete messages.
.. _struct-I2NPMessageHeader:
I2NP message header
-------------------
Description
```````````
Common header to all I2NP messages, which contains important information like a checksum, expiration date, etc.
Contents
````````
1 byte [Integer]_ specifying the type of this message, followed by a 4 byte
[Integer]_ specifying the message-id. After that there is an expiration
[Date]_, followed by a 2 byte [Integer]_ specifying the length of the message
payload, followed by a [Hash]_, which is truncated to the first byte. After
that the actual message data follows.
.. raw:: html
{% highlight lang='dataspec' %}
Standard (16 bytes):
+----+----+----+----+----+----+----+----+
|type| msg_id | expiration
+----+----+----+----+----+----+----+----+
| size |chks|
+----+----+----+----+----+----+----+----+
Short (SSU, 5 bytes):
+----+----+----+----+----+
|type| short_expiration |
+----+----+----+----+----+
Short (NTCP2, 9 bytes):
+----+----+----+----+----+----+----+----+
|type| msg_id | short_expira-
+----+----+----+----+----+----+----+----+
tion|
+----+
type :: `Integer`
length -> 1 byte
purpose -> identifies the message type (see table below)
msg_id :: `Integer`
length -> 4 bytes
purpose -> uniquely identifies this message (for some time at least)
This is usually a locally-generated random number, but
for outgoing tunnel build messages it may be derived from
the incoming message. See below.
expiration :: `Date`
8 bytes
date this message will expire
short_expiration :: `Integer`
4 bytes
date this message will expire (seconds since the epoch)
size :: `Integer`
length -> 2 bytes
purpose -> length of the payload
chks :: `Integer`
length -> 1 byte
purpose -> checksum of the payload
SHA256 hash truncated to the first byte
data ::
length -> $size bytes
purpose -> actual message contents
{% endhighlight %}
Notes
`````
* When transmitted over [SSU]_, the 16-byte standard header is not used. Only a
1-byte type and a 4-byte expiration in seconds are included. The message id
and size are incorporated in the SSU data packet format.
The checksum is not required since errors are caught in decryption.
* When transmitted over [NTCP2]_, the 16-byte standard header is not used. Only a
1-byte type, 4-byte message id, and a 4-byte expiration in seconds are included.
The size is incorporated in the NTCP2 data packet format.
The checksum is not required since errors are caught in decryption.
* The standard header is also required for I2NP messages contained in other
messages and structures (Data, TunnelData, TunnelGateway, and GarlicClove).
As of release 0.8.12, to reduce overhead, checksum verification is disabled
at some places in the protocol stack. However, for compatibility with older
versions, checksum generation is still required. It is a topic for future
research to determine points in the protocol stack where the far-end router's
version is known and checksum generation can be disabled.
* The short expiration is unsigned and will wrap around on Feb. 7, 2106. As of
that date, an offset must be added to get the correct time.
.. _struct-BuildRequestRecord:
BuildRequestRecord
------------------
Description
```````````
One Record in a set of multiple records to request the creation of one hop in
the tunnel. For more details see the tunnel overview [TUNNEL-IMPL]_ and the
tunnel creation specification [TUNNEL-CREATION]_.
Contents
````````
[TunnelId]_ to receive messages on, followed by the [Hash]_ of our
[RouterIdentity]_. After that the [TunnelId]_ and the [Hash]_ of the next
router's [RouterIdentity]_ follow.
Definition
``````````
ElGamal and AES encrypted:
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| encrypted data... |
~ ~
| |
+----+----+----+----+----+----+----+----+
encrypted_data :: ElGamal and AES encrypted data
length -> 528
total length: 528
{% endhighlight %}
ElGamal encrypted:
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| toPeer |
+ +
| |
+----+----+----+----+----+----+----+----+
| encrypted data... |
~ ~
| |
+----+----+----+----+----+----+----+----+
toPeer :: First 16 bytes of the SHA-256 Hash of the peer's `RouterIdentity`
length -> 16 bytes
encrypted_data :: ElGamal-2048 encrypted data (see notes)
length -> 512
total length: 528
{% endhighlight %}
Cleartext:
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| receive_tunnel | our_ident |
+----+----+----+----+ +
| |
+ +
| |
+ +
| |
+ +----+----+----+----+
| | next_tunnel |
+----+----+----+----+----+----+----+----+
| next_ident |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| layer_key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| iv_key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| reply_key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| reply_iv |
+ +
| |
+----+----+----+----+----+----+----+----+
|flag| request_time | send_msg_id
+----+----+----+----+----+----+----+----+
| |
+----+ +
| 29 bytes padding |
+ +
| |
+ +----+----+
| |
+----+----+----+----+----+----+
receive_tunnel :: `TunnelId`
length -> 4 bytes
nonzero
our_ident :: `Hash`
length -> 32 bytes
next_tunnel :: `TunnelId`
length -> 4 bytes
nonzero
next_ident :: `Hash`
length -> 32 bytes
layer_key :: `SessionKey`
length -> 32 bytes
iv_key :: `SessionKey`
length -> 32 bytes
reply_key :: `SessionKey`
length -> 32 bytes
reply_iv :: data
length -> 16 bytes
flag :: `Integer`
length -> 1 byte
request_time :: `Integer`
length -> 4 bytes
Hours since the epoch, i.e. current time / 3600
send_message_id :: `Integer`
length -> 4 bytes
padding :: Data
length -> 29 bytes
source -> random
total length: 222
{% endhighlight %}
Notes
`````
* In the 512-byte encrypted record, the ElGamal data contains bytes 1-256 and
258-513 of the 514-byte ElGamal encrypted block [CRYPTO-ELG]_. The two
padding bytes from the block (the zero bytes at locations 0 and 257) are
removed.
* See the tunnel creation specification [TUNNEL-CREATION]_ for details on field
contents.
.. _struct-BuildResponseRecord:
BuildResponseRecord
-------------------
.. raw:: html
{% highlight lang='dataspec' %}
Encrypted:
bytes 0-527 :: AES-encrypted record (note: same size as `BuildRequestRecord`)
Unencrypted:
+----+----+----+----+----+----+----+----+
| |
+ +
| |
+ SHA-256 Hash of following bytes +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| random data... |
~ ~
| |
+ +----+
| | ret|
+----+----+----+----+----+----+----+----+
bytes 0-31 :: SHA-256 Hash of bytes 32-527
bytes 32-526 :: random data
byte 527 :: reply
total length: 528
{% endhighlight %}
Notes
`````
* The random data field could, in the future, be used to return congestion or
peer connectivity information back to the requestor.
* See the tunnel creation specification [TUNNEL-CREATION]_ for details on the
reply field.
.. _struct-GarlicClove:
.. _Garlic Cloves:
GarlicClove
-----------
.. raw:: html
{% highlight lang='dataspec' %}
Unencrypted:
+----+----+----+----+----+----+----+----+
| Delivery Instructions |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| I2NP Message |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| Clove ID | Expiration
+----+----+----+----+----+----+----+----+
| Certificate |
+----+----+----+----+----+----+----+
Delivery Instructions :: as defined below
Length varies but is typically 1, 33, or 37 bytes
I2NP Message :: Any I2NP Message
Clove ID :: 4 byte `Integer`
Expiration :: `Date` (8 bytes)
Certificate :: Always NULL in the current implementation (3 bytes total, all zeroes)
{% endhighlight %}
Notes
`````
* Cloves are never fragmented. When used in a Garlic Clove, the first bit of
the Delivery Instructions flag byte specifies encryption. If this bit is 0,
the clove is not encrypted. If 1, the clove is encrypted, and a 32 byte
Session Key immediately follows the flag byte. Clove encryption is not fully
implemented.
* See also the garlic routing specification [GARLICSPEC]_.
* Maximum length is a function of the total length of all the cloves and the
maximum length of the GarlicMessage.
* In the future, the certificate could possibly be used for a HashCash to "pay"
for the routing.
* The message can be any I2NP message (including a GarlicMessage, although that
is not used in practice). The messages used in practice are DataMessage,
DeliveryStatusMessage, and DatabaseStoreMessage.
* The Clove ID is generally set to a random number on transmit and is checked
for duplicates on receive (same message ID space as top-level Message IDs)
.. _struct-GarlicCloveDeliveryInstructions:
Garlic Clove Delivery Instructions
----------------------------------
This specification is for Delivery Instructions inside Garlic Cloves only.
Note that "Delivery Instructions" are also used inside Tunnel Messages, where
the format is significantly different. See the Tunnel Message documentation
[TMDI]_ for details. Do NOT use the following specification for Tunnel Message
Delivery Instructions!
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
|flag| |
+----+ +
| |
+ Session Key (optional) +
| |
+ +
| |
+ +----+----+----+----+--------------+
| | |
+----+ +
| |
+ To Hash (optional) +
| |
+ +
| |
+ +----+----+----+----+--------------+
| | Tunnel ID (opt) | Delay (opt)
+----+----+----+----+----+----+----+----+
|
+----+
flag ::
1 byte
Bit order: 76543210
bit 7: encrypted? Unimplemented, always 0
If 1, a 32-byte encryption session key is included
bits 6-5: delivery type
0x0 = LOCAL, 0x01 = DESTINATION, 0x02 = ROUTER, 0x03 = TUNNEL
bit 4: delay included? Not fully implemented, always 0
If 1, four delay bytes are included
bits 3-0: reserved, set to 0 for compatibility with future uses
Session Key ::
32 bytes
Optional, present if encrypt flag bit is set.
Unimplemented, never set, never present.
To Hash ::
32 bytes
Optional, present if delivery type is DESTINATION, ROUTER, or TUNNEL
If DESTINATION, the SHA256 Hash of the destination
If ROUTER, the SHA256 Hash of the router
If TUNNEL, the SHA256 Hash of the gateway router
Tunnel ID :: `TunnelId`
4 bytes
Optional, present if delivery type is TUNNEL
The destination tunnel ID
Delay :: `Integer`
4 bytes
Optional, present if delay included flag is set
Not fully implemented. Specifies the delay in seconds.
Total length: Typical length is:
1 byte for LOCAL delivery;
33 bytes for ROUTER / DESTINATION delivery;
37 bytes for TUNNEL delivery
{% endhighlight %}
Messages
========
================================== =======
Message Type
================================== =======
DatabaseStore_ 1
DatabaseLookup_ 2
DatabaseSearchReply_ 3
DeliveryStatus_ 10
Garlic_ 11
TunnelData_ 18
TunnelGateway_ 19
Data_ 20
TunnelBuild_ 21
TunnelBuildReply_ 22
VariableTunnelBuild_ 23
VariableTunnelBuildReply_ 24
Reserved 0
Reserved for experimental messages 224-254
Reserved for future expansion 255
================================== =======
.. _msg-DatabaseStore:
DatabaseStore
-------------
Description
```````````
An unsolicited database store, or the response to a successful DatabaseLookup_ Message
Contents
````````
An uncompressed LeaseSet, LeaseSet2, MetaLeaseSet, or EncryptedLeaseset, or a compressed RouterInfo
.. raw:: html
{% highlight lang='dataspec' %}
with reply token:
+----+----+----+----+----+----+----+----+
| SHA256 Hash as key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
|type| reply token | reply_tunnelId
+----+----+----+----+----+----+----+----+
| SHA256 of the gateway RouterInfo |
+----+ +
| |
+ +
| |
+ +
| |
+ +----+----+----+----+----+----+----+
| | data ...
+----+-//
with reply token == 0:
+----+----+----+----+----+----+----+----+
| SHA256 Hash as key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
|type| 0 | data ...
+----+----+----+----+----+-//
key ::
32 bytes
SHA256 hash
type ::
1 byte
type identifier
bit 0:
0 `RouterInfo`
1 `LeaseSet` or variants listed below
bits 3-1:
Through release 0.9.17, must be 0
As of release 0.9.18, ignored, reserved for future options, set to 0 for compatibility
As of release 0.9.38, the remainder of the type identifier:
0: `RouterInfo` or `LeaseSet` (types 0 or 1)
1: `LeaseSet2` (type 3)
2: `EncryptedLeaseSet` (type 5)
3: `MetaLeaseSet` (type 7)
4-7: Unsupported, invalid
bits 7-4:
Through release 0.9.17, must be 0
As of release 0.9.18, ignored, reserved for future options, set to 0 for compatibility
reply token ::
4 bytes
If greater than zero, a `DeliveryStatusMessage`
is requested with the Message ID set to the value of the Reply Token.
A floodfill router is also expected to flood the data to the closest floodfill peers
if the token is greater than zero.
reply_tunnelId ::
4 byte `TunnelId`
Only included if reply token > 0
This is the `TunnelId` of the inbound gateway of the tunnel the response should be sent to
If $reply_tunnelId is zero, the reply is sent directy to the reply gateway router.
reply gateway ::
32 bytes
Hash of the `RouterInfo` entry to reach the gateway
Only included if reply token > 0
If $reply_tunnelId is nonzero, this is the router hash of the inbound gateway
of the tunnel the response should be sent to.
If $reply_tunnelId is zero, this is the router hash the response should be sent to.
data ::
If type == 0, data is a 2-byte `Integer` specifying the number of bytes that follow,
followed by a gzip-compressed `RouterInfo`.
If type == 1, data is an uncompressed `LeaseSet`.
If type == 3, data is an uncompressed `LeaseSet2`.
If type == 5, data is an uncompressed `EncryptedLeaseSet`.
If type == 7, data is an uncompressed `MetaLeaseSet`.
{% endhighlight %}
Notes
`````
* For security, the reply fields are ignored if the message is received down a
tunnel.
* The key is the "real" hash of the RouterIdentity or Destination, NOT the
routing key.
* Types 3, 5, and 7 are as of release 0.9.38. See proposal 123 for more information.
These types should only be sent to routers with release 0.9.38 or higher.
* As an optimization to reduce connections, if the type is a LeaseSet, the
reply token is included, the reply tunnel ID is nonzero, and the
reply gateway/tunnelID pair is found in the LeaseSet as a lease,
the recipient may reroute the reply to any other lease in the LeaseSet.
.. _msg-DatabaseLookup:
DatabaseLookup
--------------
Description
```````````
A request to look up an item in the network database. The response is either a
DatabaseStore_ or a DatabaseSearchReply_.
Contents
````````
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| SHA256 hash as the key to look up |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| SHA256 hash of the routerInfo |
+ who is asking or the gateway to +
| send the reply to |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
|flag| reply_tunnelId | size | |
+----+----+----+----+----+----+----+ +
| SHA256 of key1 to exclude |
+ +
| |
+ +
| |
+ +----+
| | |
+----+----+----+----+----+----+----+ +
| SHA256 of key2 to exclude |
+ +
~ ~
+ +----+
| | |
+----+----+----+----+----+----+----+ +
| |
+ +
| Session key if reply encryption |
+ was requested +
| |
+ +----+
| |tags|
+----+----+----+----+----+----+----+----+
| |
+ +
| Session tags if reply encryption |
+ was requested +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
key ::
32 bytes
SHA256 hash of the object to lookup
from ::
32 bytes
if deliveryFlag == 0, the SHA256 hash of the routerInfo entry this
request came from (to which the reply should be
sent)
if deliveryFlag == 1, the SHA256 hash of the reply tunnel gateway (to
which the reply should be sent)
flags ::
1 byte
bit order: 76543210
bit 0: deliveryFlag
0 => send reply directly
1 => send reply to some tunnel
bit 1: encryptionFlag
through release 0.9.5, must be set to 0
as of release 0.9.6, ignored
as of release 0.9.7:
0 => send unencrypted reply
1 => send AES encrypted reply using enclosed key and tag
bits 3-2: lookup type flags
through release 0.9.5, must be set to 00
as of release 0.9.6, ignored
as of release 0.9.16:
00 => normal lookup, return `RouterInfo` or `LeaseSet` or
`DatabaseSearchReplyMessage`
Not recommended when sending to routers
with version 0.9.16 or higher.
01 => LS lookup, return `LeaseSet` or
`DatabaseSearchReplyMessage`
As of release 0.9.38, may also return a
`LeaseSet2`, `MetaLeaseSet`, or `EncryptedLeaseSet`.
10 => RI lookup, return `RouterInfo` or
`DatabaseSearchReplyMessage`
11 => exploration lookup, return `DatabaseSearchReplyMessage`
containing non-floodfill routers only (replaces an
excludedPeer of all zeroes)
bit 4: ECIESFlag
before release 0.9.46 ignored
as of release 0.9.46:
0 => send unencrypted or ElGamal reply
1 => send ChaCha/Poly encrypted reply using enclosed key
(whether tag is enclosed depends on bit 1)
bits 7-5:
through release 0.9.5, must be set to 0
as of release 0.9.6, ignored, set to 0 for compatibility with
future uses and with older routers
reply_tunnelId ::
4 byte `TunnelID`
only included if deliveryFlag == 1
tunnelId of the tunnel to send the reply to
size ::
2 byte `Integer`
valid range: 0-512
number of peers to exclude from the `DatabaseSearchReplyMessage`
excludedPeers ::
$size SHA256 hashes of 32 bytes each (total $size*32 bytes)
if the lookup fails, these peers are requested to be excluded
from the list in the `DatabaseSearchReplyMessage`.
if excludedPeers includes a hash of all zeroes, the request is
exploratory, and the `DatabaseSearchReplyMessage` is requested
to list non-floodfill routers only.
reply_key ::
32 byte key
see below
tags ::
1 byte `Integer`
valid range: 1-32 (typically 1)
the number of reply tags that follow
see below
reply_tags ::
one or more 8 or 32 byte session tags (typically one)
see below
{% endhighlight %}
Reply Encryption
````````````````
Flag bit 4 is used in combination with bit 1 to determine the reply encryption mode.
Flag bit 4 must only be set when sending to routers with version 0.9.46 or higher.
See proposal 154 for details.
============= ========= ========= ====== === =======
Flag bits 4,1 From Dest To Router Reply DH? notes
============= ========= ========= ====== === =======
0 0 Any Any no enc no
0 1 ElG ElG AES no As of 0.9.7
1 0 ECIES ElG AEAD no As of 0.9.46
1 1 ECIES ECIES AEAD yes TBD
============= ========= ========= ====== === =======
No Encryption
``````````````
reply_key, tags, and reply_tags are not present.
ElG to ElG
``````````````
Supported as of 0.9.7.
ElG destination sends a lookup to a ElG router.
Requester key generation:
.. raw:: html
{% highlight lang='dataspec' %}
reply_key :: CSRNG(32) 32 bytes random data
reply_tags :: Each is CSRNG(32) 32 bytes random data
{% endhighlight %}
Message format:
.. raw:: html
{% highlight lang='dataspec' %}
reply_key ::
32 byte `SessionKey` big-endian
only included if encryptionFlag == 1 AND ECIESFlag == 0, only as of release 0.9.7
tags ::
1 byte `Integer`
valid range: 1-32 (typically 1)
the number of reply tags that follow
only included if encryptionFlag == 1 AND ECIESFlag == 0, only as of release 0.9.7
reply_tags ::
one or more 32 byte `SessionTag`s (typically one)
only included if encryptionFlag == 1 AND ECIESFlag == 0, only as of release 0.9.7
{% endhighlight %}
ECIES to ElG
``````````````
Supported as of 0.9.46.
ECIES destination sends a lookup to a ElG router.
The reply_key and reply_tags fields are redefined for an ECIES-encrypted reply.
Requester key generation:
.. raw:: html
{% highlight lang='dataspec' %}
reply_key :: CSRNG(32) 32 bytes random data
reply_tags :: Each is CSRNG(8) 8 bytes random data
{% endhighlight %}
Message format:
Redefine reply_key and reply_tags fields as follows:
.. raw:: html
{% highlight lang='dataspec' %}
reply_key ::
32 byte ECIES `SessionKey` big-endian
only included if encryptionFlag == 0 AND ECIESFlag == 1, only as of release 0.9.46
tags ::
1 byte `Integer`
required value: 1
the number of reply tags that follow
only included if encryptionFlag == 0 AND ECIESFlag == 1, only as of release 0.9.46
reply_tags ::
an 8 byte ECIES `SessionTag`
only included if encryptionFlag == 0 AND ECIESFlag == 1, only as of release 0.9.46
{% endhighlight %}
The reply is an ECIES Existing Session message, as defined in [ECIES]_.
Reply format
````````````
This is the existing session message,
same as in [ECIES]_, copied below for reference.
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| Session Tag |
+----+----+----+----+----+----+----+----+
| |
+ Payload Section +
| ChaCha20 encrypted data |
~ ~
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| Poly1305 Message Authentication Code |
+ (MAC) +
| 16 bytes |
+----+----+----+----+----+----+----+----+
Session Tag :: 8 bytes, cleartext
Payload Section encrypted data :: remaining data minus 16 bytes
MAC :: Poly1305 message authentication code, 16 bytes
{% endhighlight %}
AEAD parameters:
.. raw:: html
{% highlight lang='dataspec' %}
tag :: 8 byte reply_tag
k :: 32 byte session key
The reply_key.
n :: 0
ad :: The 8 byte reply_tag
payload :: Plaintext data, the DSM or DSRM.
ciphertext = ENCRYPT(k, n, payload, ad)
{% endhighlight %}
ECIES to ECIES
``````````````
This option is not yet fully defined.
ECIES routers do not yet exist and there is no documented proposal
for ECIES routers at this time.
See proposal 154.
Notes
`````
* Prior to 0.9.16, the key may be for a RouterInfo or LeaseSet, as they are in
the same key space, and there was no flag to request only a particular type
of data.
* Encryption flag, reply key, and reply tags as of release 0.9.7.
* Encrypted replies are only useful when the response is through a tunnel.
* The number of included tags could be greater than one if alternative DHT
lookup strategies (for example, recursive lookups) are implemented.
* The lookup key and exclude keys are the "real" hashes, NOT routing keys.
* Types 3, 5, and 7 may be returned as of release 0.9.38. See proposal 123 for more information.
.. _msg-DatabaseSearchReply:
DatabaseSearchReply
-------------------
Description
```````````
The response to a failed DatabaseLookup_ Message
Contents
````````
A list of router hashes closest to the requested key
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| SHA256 hash as query key |
+ +
| |
+ +
| |
+ +
| |
+----+----+----+----+----+----+----+----+
| num| peer_hashes |
+----+ +
| |
+ +
| |
+ +
| |
+ +----+----+----+----+----+----+----+
| | from |
+----+ +
| |
+ +
| |
+ +
| |
+ +----+----+----+----+----+----+----+
| |
+----+
key ::
32 bytes
SHA256 of the object being searched
num ::
1 byte `Integer`
number of peer hashes that follow, 0-255
peer_hashes ::
$num SHA256 hashes of 32 bytes each (total $num*32 bytes)
SHA256 of the `RouterIdentity` that the other router thinks is close
to the key
from ::
32 bytes
SHA256 of the `RouterInfo` of the router this reply was sent from
{% endhighlight %}
Notes
`````
* The 'from' hash is unauthenticated and cannot be trusted.
* The returned peer hashes are not necessarily closer to the key than the
router being queried.
* Typical number of hashes returned: 3
* The lookup key, peer hashes, and from hash are "real" hashes, NOT routing
keys.
.. _msg-DeliveryStatus:
DeliveryStatus
--------------
Description
```````````
A simple message acknowledgment. Generally created by the message originator,
and wrapped in a Garlic Message with the message itself, to be returned by the
destination.
Contents
````````
The ID of the delivered message, and the creation or arrival time.
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+----+----+----+----+
| msg_id | time_stamp |
+----+----+----+----+----+----+----+----+----+----+----+----+
msg_id :: `Integer`
4 bytes
unique ID of the message we deliver the DeliveryStatus for (see
`I2NPMessageHeader` for details)
time_stamp :: `Date`
8 bytes
time the message was successfully created or delivered
{% endhighlight %}
Notes
`````
* It appears that the time stamp is always set by the creator to the current
time. However there are several uses of this in the code, and more may be
added in the future.
* This message is also used as a session established confirmation in SSU
[SSU-ED]_. In this case, the message ID is set to a random number, and the
"arrival time" is set to the current network-wide ID, which is 2 (i.e.
0x0000000000000002).
.. _msg-Garlic:
Garlic
------
Description
```````````
Used to wrap multiple encrypted I2NP Messages
Contents
````````
When decrypted, a series of `Garlic Cloves`_ and additional
data, also known as a Clove Set.
Encrypted:
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| length | data |
+----+----+----+----+ +
| |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
length ::
4 byte `Integer`
number of bytes that follow 0 - 64 KB
data ::
$length bytes
ElGamal encrypted data
{% endhighlight %}
Decrypted data, also known as a Clove Set:
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| num| clove 1 |
+----+ +
| |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| clove 2 ... |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| Certificate | Message_ID |
+----+----+----+----+----+----+----+----+
Expiration |
+----+----+----+----+----+----+----+
num ::
1 byte `Integer` number of `GarlicClove`s to follow
clove :: a `GarlicClove`
Certificate :: always NULL in the current implementation (3 bytes total, all zeroes)
Message_ID :: 4 byte `Integer`
Expiration :: `Date` (8 bytes)
{% endhighlight %}
Notes
`````
* When unencrypted, data contains one or more `Garlic Cloves`_.
* The AES encrypted block is padded to a minimum of 128 bytes; with the 32-byte
Session Tag the minimum size of the encrypted message is 160 bytes; with the
4 length bytes the minimum size of the Garlic Message is 164 bytes.
* Actual max length is less than 64 KB; see [I2NP]_.
* See also the ElGamal/AES specification [ELG-AES]_.
* See also the garlic routing specification [GARLIC]_.
* The 128 byte minimum size of the AES encrypted block is not currently
configurable, however the minimum size of a DataMessage in a GarlicClove in a
GarlicMessage, with overhead, is 128 bytes anyway. A configurable option to
increase the minimum size may be added in the future.
* The message ID is generally set to a random number on transmit and appears to
be ignored on receive.
* In the future, the certificate could possibly be used for a HashCash to "pay"
for the routing.
.. _msg-TunnelData:
TunnelData
----------
Description
```````````
A message sent from a tunnel's gateway or participant to the next participant
or endpoint. The data is of fixed length, containing I2NP messages that are
fragmented, batched, padded, and encrypted.
Contents
````````
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| tunnnelID | data |
+----+----+----+----+ |
| |
~ ~
~ ~
| |
+ +----+----+----+----+
| |
+----+----+----+----+
tunnelId ::
4 byte `TunnelId`
identifies the tunnel this message is directed at
data ::
1024 bytes
payload data.. fixed to 1024 bytes
{% endhighlight %}
Notes
`````
* The I2NP message ID for this message is set to a new random number at each
hop.
* See also the Tunnel Message Specification [TUNNEL-MSG]_
.. _msg-TunnelGateway:
TunnelGateway
-------------
Description
```````````
Wraps another I2NP message to be sent into a tunnel at the tunnel's inbound gateway.
Contents
````````
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+-//
| tunnelId | length | data...
+----+----+----+----+----+----+----+-//
tunnelId ::
4 byte `TunnelId`
identifies the tunnel this message is directed at
length ::
2 byte `Integer`
length of the payload
data ::
$length bytes
actual payload of this message
{% endhighlight %}
Notes
`````
* The payload is an I2NP message with a standard 16-byte header.
.. _msg-Data:
Data
----
Description
```````````
Used by Garlic Messages and Garlic Cloves to wrap arbitrary data.
Contents
````````
A length Integer, followed by opaque data.
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+-//-+
| length | data... |
+----+----+----+----+----+-//-+
length ::
4 bytes
length of the payload
data ::
$length bytes
actual payload of this message
{% endhighlight %}
Notes
`````
* This message contains no routing information and will never be sent
"unwrapped". It is only used inside `Garlic` messages.
.. _msg-TunnelBuild:
TunnelBuild
-----------
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| Record 0 ... |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| Record 1 ... |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
| Record 7 ... |
~ ~
~ ~
| |
+----+----+----+----+----+----+----+----+
Just 8 `BuildRequestRecord`s attached together
record size: 528 bytes
total size: 8*528 = 4224 bytes
{% endhighlight %}
Notes
`````
* See also the tunnel creation specification [TUNNEL-CREATION]_.
* The I2NP message ID for this message must be set according to the tunnel
creation specification.
* While this message is rarely seen in today's network, having been replaced by
the `VariableTunnelBuild` message, it may still be used for very long tunnels,
and has not been deprecated. Routers must implement.
.. _msg-TunnelBuildReply:
TunnelBuildReply
----------------
.. raw:: html
{% highlight lang='dataspec' %}
Same format as `TunnelBuildMessage`, with `BuildResponseRecord`s
{% endhighlight %}
Notes
`````
* See also the tunnel creation specification [TUNNEL-CREATION]_.
* The I2NP message ID for this message must be set according to the tunnel
creation specification.
* While this message is rarely seen in today's network, having been replaced by
the `VariableTunnelBuildReply` message, it may still be used for very long
tunnels, and has not been deprecated. Routers must implement.
.. _msg-VariableTunnelBuild:
VariableTunnelBuild
-------------------
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| num| BuildRequestRecords...
+----+----+----+----+----+----+----+----+
Same format as `TunnelBuildMessage`, except for the addition of a $num field
in front and $num number of `BuildRequestRecord`s instead of 8
num ::
1 byte `Integer`
Valid values: 1-8
record size: 528 bytes
total size: 1+$num*528
{% endhighlight %}
Notes
`````
* This message was introduced in router version 0.7.12, and may not be sent to
tunnel participants earlier than that version.
* See also the tunnel creation specification [TUNNEL-CREATION]_.
* The I2NP message ID for this message must be set according to the tunnel
creation specification.
* Typical number of records in today's network is 5.
.. _msg-VariableTunnelBuildReply:
VariableTunnelBuildReply
------------------------
.. raw:: html
{% highlight lang='dataspec' %}
+----+----+----+----+----+----+----+----+
| num| BuildResponseRecords...
+----+----+----+----+----+----+----+----+
Same format as `VariableTunnelBuildMessage`, with `BuildResponseRecord`s.
{% endhighlight %}
Notes
`````
* This message was introduced in router version 0.7.12, and may not be sent to
tunnel participants earlier than that version.
* See also the tunnel creation specification [TUNNEL-CREATION]_.
* The I2NP message ID for this message must be set according to the tunnel
creation specification.
* Typical number of records in today's network is 5.
References
==========
.. [CRYPTO-ELG]
{{ site_url('docs/how/cryptography', True) }}#elgamal
.. [Date]
{{ ctags_url('Date') }}
.. [ECIES]
{{ proposal_url('144') }}
.. [ElG-AES]
{{ site_url('docs/how/elgamal-aes', True) }}
.. [GARLICSPEC]
{{ site_url('docs/how/garlic-routing', True) }}
.. [Hash]
{{ ctags_url('Hash') }}
.. [I2NP]
{{ site_url('docs/protocol/i2np', True) }}
.. [Integer]
{{ ctags_url('Integer') }}
.. [NTCP2]
{{ spec_url('ntcp2') }}
.. [RouterIdentity]
{{ ctags_url('RouterIdentity') }}
.. [SSU]
{{ site_url('docs/transport/ssu', True) }}
.. [SSU-ED]
{{ site_url('docs/transport/ssu', True) }}#establishDirect
.. [TMDI]
{{ ctags_url('TunnelMessageDeliveryInstructions') }}
.. [TUNNEL-CREATION]
{{ spec_url('tunnel-creation') }}
.. [TUNNEL-MSG]
{{ spec_url('tunnel-message') }}
.. [TUNNEL-IMPL]
{{ site_url('docs/tunnels/implementation', True) }}
.. [TunnelId]
{{ ctags_url('TunnelId') }}
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