[taler-wallet-kotlin] 02/02: Implement setupRefreshPlanchet

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torsten-grote pushed a commit to branch master
in repository wallet-kotlin.

commit 504e4e90fa7e2b2da2d1b8cda3baef3b38290a84
Author: Torsten Grote <t@grobox.de>
AuthorDate: Mon Jun 8 09:53:34 2020 -0300

    Implement setupRefreshPlanchet
---
 .idea/dictionaries/user.xml                           |  1 +
 .../kotlin/net/taler/wallet/kotlin/crypto/Crypto.kt   |  2 ++
 .../net/taler/wallet/kotlin/crypto/CryptoImpl.kt      | 19 +++++++++++++++++++
 3 files changed, 22 insertions(+)

diff --git a/.idea/dictionaries/user.xml b/.idea/dictionaries/user.xml
index 5f88694..a7b3027 100644
--- a/.idea/dictionaries/user.xml
+++ b/.idea/dictionaries/user.xml
@@ -5,6 +5,7 @@
       <w>eddsa</w>
       <w>hmac</w>
       <w>nacl</w>
+      <w>planchet</w>
     </words>
   </dictionary>
 </component>
\ No newline at end of file
diff --git a/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Crypto.kt 
b/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Crypto.kt
index a55c91d..ba43c18 100644
--- a/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Crypto.kt
+++ b/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/Crypto.kt
@@ -15,10 +15,12 @@ internal interface Crypto {
     fun rsaBlind(hm: ByteArray, bks: ByteArray, rsaPubEnc: ByteArray): 
ByteArray
     fun rsaUnblind(sig: ByteArray, rsaPubEnc: ByteArray, bks: ByteArray): 
ByteArray
     fun rsaVerify(hm: ByteArray, rsaSig: ByteArray, rsaPubEnc: ByteArray): 
Boolean
+    fun setupRefreshPlanchet(secretSeed: ByteArray, coinNumber: Int): FreshCoin
 }
 
 class EddsaKeyPair(val privateKey: ByteArray, val publicKey: ByteArray)
 class EcdheKeyPair(val privateKey: ByteArray, val publicKey: ByteArray)
+class FreshCoin(val coinPublicKey: ByteArray, coinPrivateKey: ByteArray, bks: 
ByteArray)
 
 internal expect object CryptoFactory {
     internal fun getCrypto(): Crypto
diff --git a/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/CryptoImpl.kt 
b/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/CryptoImpl.kt
index ae333eb..a21c156 100644
--- a/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/CryptoImpl.kt
+++ b/src/commonMain/kotlin/net/taler/wallet/kotlin/crypto/CryptoImpl.kt
@@ -6,4 +6,23 @@ abstract class CryptoImpl : Crypto {
         return Kdf.kdf(outputLength, ikm, salt, info, { sha256(it) }, { 
sha512(it) })
     }
 
+    override fun setupRefreshPlanchet(secretSeed: ByteArray, coinNumber: Int): 
FreshCoin {
+        val info = "taler-coin-derivation".encodeToByteArray()
+        val salt = coinNumber.toByteArray()
+        val out = kdf(64, secretSeed, salt, info)
+        val coinPriv = out.copyOfRange(0, 32)
+        val bks = out.copyOfRange(32, 64)
+        return FreshCoin(bks, coinPriv, eddsaGetPublic(coinPriv))
+    }
+
+    // TODO check if this is the correct coinNumber to ByteArray conversion
+    private fun Int.toByteArray(): ByteArray {
+        val bytes = ByteArray(4)
+        bytes[3] = (this and 0xFFFF).toByte()
+        bytes[2] = ((this ushr 8) and 0xFFFF).toByte()
+        bytes[1] = ((this ushr 16) and 0xFFFF).toByte()
+        bytes[0] = ((this ushr 24) and 0xFFFF).toByte()
+        return bytes
+    }
+
 }

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