PBKD semi ready, before key refactoring

src/commonMain/kotlin/net/sergeych/crypto2/PBKD.kt

@@ -2,7 +2,6 @@ package net.sergeych.crypto2
 
 import com.ionspin.kotlin.crypto.util.encodeToUByteArray
 import kotlinx.serialization.Serializable
-import kotlinx.serialization.Transient
 import net.sergeych.bipack.BipackEncoder
 import net.sergeych.bipack.Unsigned
 import net.sergeych.synctools.ProtectedOp
@@ -10,17 +9,31 @@ import net.sergeych.synctools.invoke
 
 object PBKD {
 
+    /**
+     * Parameters to generate a reasonably secure data bytes with [deriveUBytes] or a [SymmetricKey]
+     * with [deriveKey]
+     */
     @Serializable
     class Params(
         val kdf: KDF,
         @Unsigned
         val startOffset: Int,
-        @Transient
-        private var precalculatedKey: SymmetricKey?=null
+        @Unsigned
+        val length: Int,
     ) {
 
         /**
-         * Derive a key from the password in the idempotent manner.
+         * Derive UByteArray from the password in the idempotent way.
+         * Could be used to construct keys, IVs, tokens, whatever.
+         * Most often [deriveKey] is used instead which derives the key.
+         */
+        fun deriveUBytes(password: String): UByteArray {
+            val bytes = generate(kdf, password)
+            return bytes.sliceArray(startOffset..<startOffset + length)
+        }
+
+        /**
+         * Derive a new key from the password in the idempotent manner.
          * If the [keyId] is provided, it will be used to determine key type (otherwise default asymmetric)
          * and to check the result, and the exception will be thrown.
          *
@@ -31,10 +44,7 @@ object PBKD {
          * @param keyId optional key id, to get a key type from and check the result
          * @throws IncorrectPasswordException if [keyId] is provided and does not match the derivation result
          */
-        fun derive(password: String, keyId: KeyId? = null): SymmetricKey {
-            // could be already calculated
-            precalculatedKey?.let { return it }
-
+        fun deriveKey(password: String, keyId: KeyId? = null): SymmetricKey {
             // check key id sanity
             keyId?.let {
                 if (it.id.magick != KeysMagickNumber.defaultSymmetric.number) {
@@ -42,28 +52,36 @@ object PBKD {
                 }
             }
             // this will not be ok when we support other key types:
-            val keySize = SymmetricKey.keyLength
+            if (SymmetricKey.keyLength != length)
+                throw NotSupportedException("can't create key from $length byte(s), required ${SymmetricKey.keyLength}")
 
             // derive
-            val bytes = generate(kdf, password)
-            val key = SymmetricKey(bytes.sliceArray(startOffset..<startOffset + keySize), this)
+            val key = SymmetricKey(
+                deriveUBytes(password)
+                    .sliceArray(startOffset..<startOffset + SymmetricKey.keyLength),
+                this
+            )
 
-            // check if we can checking
-            if( keyId != null && keyId != key.id )
+            // check if we can
+            if (keyId != null && keyId != key.id)
                 throw IncorrectPasswordException()
 
-            // save for later
-            precalculatedKey = key
-
             return key
         }
     }
 
     /**
-     * Create [PBKD.Params] to derive several keys from the single password
+     * Derive several keys-suitable params
      */
-    fun createMutlipleParams(complexity: KDF.Complexity,keysCount: Int): List<Params> {
-        TODO()
+    fun deriveMultipleKeys(password: String,keysCount: Int,
+                           complexity: KDF.Complexity = KDF.Complexity.Moderate,
+                           salt: UByteArray = KDF.Argon.randomSalt()
+    ): List<SymmetricKey> {
+        require(keysCount > 0) { "keysCount must be positive" }
+        val keyLength = SymmetricKey.keyLength
+        val totalSize = keysCount * keyLength
+        val kdf = KDF.Argon.create(complexity, salt, totalSize)
+        return (0 ..< keysCount).map { Params(kdf, it*keyLength, keyLength).deriveKey(password) }
     }
 
     private val op = ProtectedOp()

src/commonMain/kotlin/net/sergeych/crypto2/kdf.kt

@@ -55,10 +55,8 @@ sealed class KDF {
             }
         }
 
-        override fun derive(password: String): UByteArray {
-            TODO()
-            //PasswordHash.pwhash(keySize, )
-        }
+        override fun derive(password: String): UByteArray =
+            PasswordHash.pwhash(keySize, password, salt, instructionsComplexity, memComplexity, algorithm.code)
 
         override fun equals(other: Any?): Boolean {
             if (this === other) return true