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Prop. 157 KDF cleanups

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zzz
2021-07-12 15:31:22 -04:00
parent 5a1ccb81c7
commit 29febb8712
1 changed files with 17 additions and 16 deletions
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33
i2p2www/spec/proposals/157-new-tbm.rst
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@@ -393,7 +393,7 @@ bytes 0-201: ChaCha20 encrypted ShortBuildReplyRecord
KDF KDF
----------------------- -----------------------
TBD See KDF section below.
@@ -494,7 +494,7 @@ KDF
--- ---
We use ck from Noise state after tunnel build record encryption/decrytion We use ck from Noise state after tunnel build record encryption/decrytion
to derivve following keys: reply key, AES layer key, AES iv key and garlic reply key/tag for OBEP. to derive following keys: reply key, AES layer key, AES IV key and garlic reply key/tag for OBEP.
Reply key: Reply key:
Unlike long records we can't use left part of ck for reply key, because it's not last and will be used later. Unlike long records we can't use left part of ck for reply key, because it's not last and will be used later.
@@ -504,29 +504,30 @@ Both use the same key, nonce is record's position in the message starring from 0
.. raw:: html .. raw:: html
{% highlight lang='dataspec' %} {% highlight lang='dataspec' %}
ck = HKDF(ck, ZEROLEN, "SMTunnelReplyKey", 64) keydata = HKDF(ck, ZEROLEN, "SMTunnelReplyKey", 64)
replyKey = ck[32:63] replyKey = keydata[32:63]
ck = keydata[0:31]
Layer key: Layer key:
Layer key is always AES for now, but same KDF can be used from Chacha20 Layer key is always AES for now, but same KDF can be used from Chacha20
ck = HKDF(ck, ZEROLEN, "SMTunnelLayerKey", 64) keydata = HKDF(ck, ZEROLEN, "SMTunnelLayerKey", 64)
replyKey = ck[32:63] layerKey = keydata[32:63]
IV key: IV key for non-OBEP record:
For non_OBEP record ivKey = keydata[0:31]
ivKey = ck[0:32]
because it's last because it's last
for OBEP record IV key for OBEP record:
ck = HKDF(ck, ZEROLEN, "TunnelLayerIVKey", 64) ck = keydata[0:31]
ivKey = ck[32:63] keydata = HKDF(ck, ZEROLEN, "TunnelLayerIVKey", 64)
ivKey = keydata[32:63]
ck = keydata[0:31]
OBEP garlic reply key/tag: OBEP garlic reply key/tag:
ck = HKDF(ck, ZEROLEN, "RGarlicKeyAndTag", 64) keydata = HKDF(ck, ZEROLEN, "RGarlicKeyAndTag", 64)
key = ck[32:64] replyKey = keydata[32:63]
tag = ck[0:8] replyTag = keydata[0:7]
{% endhighlight %} {% endhighlight %}