1 files changed, 87 insertions, 0 deletions
diff --git a/wallet/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Planchet.kt b/wallet/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Planchet.kt
new file mode 100644
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--- /dev/null
+++ b/wallet/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Planchet.kt
@@ -0,0 +1,87 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.wallet.kotlin.crypto
+
+import net.taler.wallet.kotlin.Amount
+import net.taler.wallet.kotlin.Base32Crockford
+
+internal class Planchet(private val crypto: Crypto) {
+
+    data class CreationRequest(
+        val value: Amount,
+        val feeWithdraw: Amount,
+        val denomPub: String,
+        val reservePub: String,
+        val reservePriv: String
+    )
+
+    data class CreationResult(
+        val coinPub: String,
+        val coinPriv: String,
+        val reservePub: String,
+        val denomPubHash: String,
+        val denomPub: String,
+        val blindingKey: String,
+        val withdrawSig: String,
+        val coinEv: String,
+        val coinValue: Amount,
+        val coinEvHash: String
+    )
+
+    internal fun create(req: CreationRequest, coinKeyPair: EddsaKeyPair, blindingFactor: ByteArray): CreationResult {
+        val reservePub = Base32Crockford.decode(req.reservePub)
+        val reservePriv = Base32Crockford.decode(req.reservePriv)
+        val denomPub = Base32Crockford.decode(req.denomPub)
+        val coinPubHash = crypto.sha512(coinKeyPair.publicKey)
+        val ev = crypto.rsaBlind(coinPubHash, blindingFactor, denomPub)
+        val amountWithFee = req.value + req.feeWithdraw
+        val denomPubHash = crypto.sha512(denomPub)
+        val evHash = crypto.sha512(ev)
+
+        val withdrawRequest = Signature.PurposeBuilder(Signature.RESERVE_WITHDRAW)
+            .put(reservePub)
+            .put(amountWithFee.toByteArray())
+            .put(req.feeWithdraw.toByteArray())
+            .put(denomPubHash)
+            .put(evHash)
+            .build()
+
+        val sig = crypto.eddsaSign(withdrawRequest, reservePriv)
+        return CreationResult(
+            blindingKey = Base32Crockford.encode(blindingFactor),
+            coinEv = Base32Crockford.encode(ev),
+            coinPriv = Base32Crockford.encode(coinKeyPair.privateKey),
+            coinPub = Base32Crockford.encode(coinKeyPair.publicKey),
+            coinValue = req.value,
+            denomPub = req.denomPub,
+            denomPubHash = Base32Crockford.encode(denomPubHash),
+            reservePub = req.reservePub,
+            withdrawSig = Base32Crockford.encode(sig),
+            coinEvHash = Base32Crockford.encode(evHash)
+        )
+    }
+
+    /**
+     * Create a pre-coin ([Planchet]) of the given [CreationRequest].
+     */
+    fun create(req: CreationRequest): CreationResult {
+        val coinKeyPair = crypto.createEddsaKeyPair()
+        val blindingFactor = crypto.getRandomBytes(32)
+        return create(req, coinKeyPair, blindingFactor)
+    }
+
+}