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Prop. 144 next key fixes and clarifications

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zzz
2020-04-25 12:49:01 +00:00
parent 16189ed6fe
commit ea39c0d3ed
1 changed files with 74 additions and 51 deletions
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i2p2www/spec/proposals/144-ecies-x25519-aead-ratchet.rst
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@@ -5,7 +5,7 @@ ECIES-X25519-AEAD-Ratchet
:author: zzz, chisana :author: zzz, chisana
:created: 2018-11-22 :created: 2018-11-22
:thread: http://zzz.i2p/topics/2639 :thread: http://zzz.i2p/topics/2639
:lastupdated: 2020-04-22 :lastupdated: 2020-04-25
:status: Open :status: Open
:target: 0.9.46 :target: 0.9.46
:implementedin: 0.9.46 :implementedin: 0.9.46
@@ -1939,68 +1939,89 @@ by initiating the key exchange; the diagram below shows that.
When Alice ratchets, the same thing happens in reverse. When Alice ratchets, the same thing happens in reverse.
The first tag set used after the NS/NSR handshake is tag set 0. The first tag set used after the NS/NSR handshake is tag set 0.
When that tag set is almost exhausted, new keys must be exchanged to create tag set 1. When tag set 0 is almost exhausted, new keys must be exchanged in both directions to create tag set 1.
After that, a new key is only sent in one direction. After that, a new key is only sent in one direction.
For tag set 2, Bob sends the ID of his old key and requests a new key from Alice.
To create tag set 2, the tag sender sends a new key and the tag receiver sends the ID of his old key as an acknowledgement.
Both sides do a DH. Both sides do a DH.
For tag set 3, Bob sends a new key and Alice sends the ID of her old key. To create tag set 3, the tag sender sends the ID of his old key and requests a new key from the tag receiver.
Both sides do a DH. Both sides do a DH.
Subsequent tag sets are generated as for tag sets 2 and 3. Subsequent tag sets are generated as for tag sets 2 and 3.
The tag set number is (1 + Alice's key id + Bob's key id). The tag set number is (1 + sender key id + receiver key id).
.. raw:: html .. raw:: html
{% highlight %} {% highlight %}
Alice Bob Tag Sender Tag Receiver
... use tag set #0 ...
(Tagset #0 almost empty) (Tagset #0 almost empty)
(generate new key #0) (generate new key #0)
<-------------- Next Key, forward, request reverse, with key #0 Next Key, forward, request reverse, with key #0 -------->
(repeat until next key received) (repeat until next key received)
(generate new key #0, do DH, create IB Tagset #1) (generate new key #0, do DH, create IB Tagset #1)
Next Key, reverse, with key #0 -------------------> <------------- Next Key, reverse, with key #0
(repeat until tag received on new tagset) (repeat until tag received on new tagset)
(do DH, create OB Tagset #1) (do DH, create OB Tagset #1)
...
(Tagset #1 almost empty)
(resend key #0)
<-------------- Next Key, forward, request reverse, id 0
... use tag set #1 ...
(Tagset #1 almost empty)
(generate new key #1)
Next Key, forward, with key #1 -------->
(repeat until next key received) (repeat until next key received)
(generate new key #1, do DH, create IB Tagset #2) (reuse key #0, do DH, create IB Tagset #2)
Next Key, reverse, with key #1 -------------------> <-------------- Next Key, reverse, id 0
(repeat until tag received on new tagset) (repeat until tag received on new tagset)
(do DH, create OB Tagset #2) (do DH, create OB Tagset #2)
...
(Tagset #2 almost empty)
(generate new key #1)
<-------------- Next Key, forward, with key #1
... use tag set #2 ...
(Tagset #2 almost empty)
(reuse key #1)
Next Key, forward, request reverse, id 1 -------->
(repeat until next key received) (repeat until next key received)
(reuse key #1, do DH, create IB Tagset #3) (generate new key #1, do DH, create IB Tagset #3)
Next Key, reverse, id 1 -------------------> <-------------- Next Key, reverse, with key #1
(repeat until tag received on new tagset)
(do DH, create OB Tagset #3) (do DH, create OB Tagset #3)
(reuse key #1, do DH, create IB Tagset #3)
Repeat the above patterns for tagsets
2 and 3.
Every even tagset, Bob resends his key ... use tag set #3 ...
and requests a reverse key from Alice.
Every odd tagset, Bob sends a new key
and Alice sends an ACK.
After tag set 3, repeat the above
patterns as shown for tag sets 2 and 3.
To create a new even-numbered tag set, the sender sends a new key
to the receiver. The receiver sends his old key ID
back as an acknowledgement.
To create a new odd-numbered tag set, the sender sends a reverse request
to the receiver. The receiver sends a new reverse key to the sender.
{% endhighlight %} {% endhighlight %}
@@ -2012,20 +2033,22 @@ the receiver should listen for tags in both tagsets, and delete the old tagset
after a short time, about 3 minutes. after a short time, about 3 minutes.
Summary of tag set and key ID progression: Summary of tag set and key ID progression is in the table below.
* indicates that a new key is generated.
========== ============= ===========
Tag Set ID Sender key ID Rcvr key ID ============== ============= ===========
========== ============= =========== New Tag Set ID Sender key ID Rcvr key ID
============== ============= ===========
0 n/a n/a 0 n/a n/a
1 0 0 1 0 * 0 *
2 1 0 2 1 * 0
3 1 1 3 1 1 *
4 2 1 4 2 * 1
5 2 2 5 2 2 *
... ... ... ... ... ...
65534 32767 32766 65534 32767 * 32766
65535 32767 32767 65535 32767 32767 *
========== ============= =========== ========== ============= ===========