commit e1ba021572d369115faebcbc03911e10bff6cbb2
parent 3167a1b8dae9ac4482988b3b417607b6ae88c0bc
Author: Mikolai Gütschow <mikolai.guetschow@tu-dresden.de>
Date: Thu, 18 Jun 2026 10:20:14 +0200
refresh: correct hkdf/random sizes
Diffstat:
2 files changed, 411 insertions(+), 411 deletions(-)
diff --git a/draft-guetschow-taler-protocol.md b/draft-guetschow-taler-protocol.md
@@ -1131,7 +1131,7 @@ and thereby that value transfer among untrusted parties can only happen via paym
~~~
Refresh-Derive(shared, i, denom) =
- planchet_seed = HKDF(uint32(i), shared, "taler-coin-derivation", 64)
+ planchet_seed = HKDF(uint32(i), shared, "taler-coin-derivation", 32)
blind_secret = HKDF("bks", planchet_seed, "", 32)
coin.priv = HKDF("coin", planchet_seed, "", 32)
coin.pub = Ed25519-GetPub(coin.priv)
@@ -1203,7 +1203,7 @@ commitment // see TALER_refresh_get_commitment
~~~ pseudocode
(W1) coin melting (wallet)
-refresh_seed = random(256)
+refresh_seed = random(512)
⟨batch_seedₖ⟩ = HKDF("refresh-batch-seeds", refresh_seed, coin.priv, k*64)
for k in 0..κ:
⟨transferₖᵢ.priv⟩ = HKDF("refresh-transfer-private-keys", batch_seedₖ, "", n*32)
diff --git a/draft-guetschow-taler-protocol.xml b/draft-guetschow-taler-protocol.xml
@@ -24,7 +24,7 @@
<email>mikolai.guetschow@tu-dresden.de</email>
</address>
</author>
- <date year="2026" month="May" day="19"/>
+ <date year="2026" month="June" day="18"/>
<workgroup>independent</workgroup>
<keyword>taler</keyword>
<keyword>cryptography</keyword>
@@ -1057,7 +1057,7 @@ The derivation ensures that ownership of coins (knowledge of the private key) is
and thereby that value transfer among untrusted parties can only happen via payment and deposit, not via refresh.</t>
<artwork><