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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
-----------------------
TBD
See KDF section below.
@@ -494,7 +494,7 @@ KDF
---
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:
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
{% highlight lang='dataspec' %}
ck = HKDF(ck, ZEROLEN, "SMTunnelReplyKey", 64)
replyKey = ck[32:63]
keydata = HKDF(ck, ZEROLEN, "SMTunnelReplyKey", 64)
replyKey = keydata[32:63]
ck = keydata[0:31]
Layer key:
Layer key is always AES for now, but same KDF can be used from Chacha20
ck = HKDF(ck, ZEROLEN, "SMTunnelLayerKey", 64)
replyKey = ck[32:63]
keydata = HKDF(ck, ZEROLEN, "SMTunnelLayerKey", 64)
layerKey = keydata[32:63]
IV key:
For non_OBEP record
ivKey = ck[0:32]
IV key for non-OBEP record:
ivKey = keydata[0:31]
because it's last
for OBEP record
ck = HKDF(ck, ZEROLEN, "TunnelLayerIVKey", 64)
ivKey = ck[32:63]
IV key for OBEP record:
ck = keydata[0:31]
keydata = HKDF(ck, ZEROLEN, "TunnelLayerIVKey", 64)
ivKey = keydata[32:63]
ck = keydata[0:31]
OBEP garlic reply key/tag:
ck = HKDF(ck, ZEROLEN, "RGarlicKeyAndTag", 64)
key = ck[32:64]
tag = ck[0:8]
keydata = HKDF(ck, ZEROLEN, "RGarlicKeyAndTag", 64)
replyKey = keydata[32:63]
replyTag = keydata[0:7]
{% endhighlight %}