From c09c5bbe625566fc61c811160d2ccdab263327fa Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Tue, 15 Dec 2020 17:12:22 +0100
Subject: derive tipping planchets from seed, implement backup further

---
 packages/taler-wallet-core/src/crypto/talerCrypto.ts | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'packages/taler-wallet-core/src/crypto/talerCrypto.ts')

diff --git a/packages/taler-wallet-core/src/crypto/talerCrypto.ts b/packages/taler-wallet-core/src/crypto/talerCrypto.ts
index 4faa523a0..095957982 100644
--- a/packages/taler-wallet-core/src/crypto/talerCrypto.ts
+++ b/packages/taler-wallet-core/src/crypto/talerCrypto.ts
@@ -390,6 +390,25 @@ export function setupRefreshPlanchet(
   };
 }
 
+export function setupTipPlanchet(
+  secretSeed: Uint8Array,
+  coinNumber: number,
+): FreshCoin {
+  const info = stringToBytes("taler-tip-coin-derivation");
+  const saltArrBuf = new ArrayBuffer(4);
+  const salt = new Uint8Array(saltArrBuf);
+  const saltDataView = new DataView(saltArrBuf);
+  saltDataView.setUint32(0, coinNumber);
+  const out = kdf(64, secretSeed, salt, info);
+  const coinPriv = out.slice(0, 32);
+  const bks = out.slice(32, 64);
+  return {
+    bks,
+    coinPriv,
+    coinPub: eddsaGetPublic(coinPriv),
+  };
+}
+
 export function setupRefreshTransferPub(
   secretSeed: Uint8Array,
   transferPubIndex: number,
-- 
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