use top-level Seal class

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

@@ -0,0 +1,11 @@
+package net.sergeych.crypto2
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+class Seal(
+    val publicKey: SigningKey.Public,
+    val signature: UByteArray
+) {
+    inline fun verify(message: UByteArray) = publicKey.verify(signature, message)
+}

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

@@ -30,14 +30,14 @@ class SignedBox(
      * _can't assume it always returns a copied object!_
      */
     operator fun plus(key: SigningKey.Secret): SignedBox =
-        if (key.verifying in this) this
-        else SignedBox(message, seals + Seal.create(key, message), false)
+        if (key.publicKey in this) this
+        else SignedBox(message, seals + key.seal(message), false)
 
     /**
      * Check that it is signed with a specified key.
      */
-    operator fun contains(verifyingKey: SigningKey.Public): Boolean {
-        return seals.any { it.key == verifyingKey }
+    operator fun contains(publicKey: SigningKey.Public): Boolean {
+        return seals.any { it.publicKey == publicKey }
     }
 
     init {
@@ -47,22 +47,6 @@ class SignedBox(
         }
     }
 
-    /**
-     * A key + signature pair for [SignedBox] boxes, usually you don't use it
-     * directly bug call [SignedBox] constructor or [SignedBox.plus] to
-     * add seals.
-     */
-    @Serializable
-    data class Seal(val key: SigningKey.Public, val signature: UByteArray) {
-
-        fun verify(message: UByteArray): Boolean = key.verify(signature, message)
-
-        companion object {
-            fun create(key: SigningKey.Secret, message: UByteArray): Seal {
-                return Seal(key.verifying, key.sign(message))
-            }
-        }
-    }
 
     companion object {
         /**
@@ -76,6 +60,6 @@ class SignedBox(
          * @throws IllegalArgumentException if keys are not specified.
          */
         operator fun invoke(data: UByteArray, vararg keys: SigningKey.Secret): SignedBox =
-            SignedBox(data, keys.map { Seal.create(it, data) }, false)
+            SignedBox(data, keys.map { it.seal(data) }, false)
     }
 }

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

@@ -54,11 +54,13 @@ sealed class SigningKey {
     @SerialName("s")
     class Secret(override val packed: UByteArray) : SigningKey() {
 
-        val verifying: Public by lazy {
+        val publicKey: Public by lazy {
             Public(Signature.ed25519SkToPk(packed))
         }
 
         fun sign(message: UByteArray): UByteArray = Signature.detached(message, packed)
+
+        fun seal(message: UByteArray): Seal = Seal(this.publicKey, sign(message))
         override fun toString(): String = "Sct:${super.toString()}"
 
         companion object {

src/commonMain/kotlin/net/sergeych/kiloparsec/KiloClientConnection.kt

@@ -59,19 +59,17 @@ class KiloClientConnection<S>(
                 var params = KiloParams(false, transport, sk, session, null, this@KiloClientConnection)
 
                 // Check ID if any
-                serverHe.serverPublicKey?.let { k ->
-                    if (serverHe.signature == null)
-                        throw RemoteInterface.SecurityException("missing signature")
-                    if (!k.verify(serverHe.signature, params.token))
+                serverHe.signature?.let { s ->
+                    if (!s.verify(params.token))
                         throw RemoteInterface.SecurityException("wrong signature")
-                    params = params.copy(remoteIdentity = k)
+                    params = params.copy(remoteIdentity = s.publicKey)
                 }
 
                 transport.call(
                     L0ClientId, params.encrypt(
                         pack(
                             ClientIdentity(
-                                secretIdKey?.verifying,
+                                secretIdKey?.publicKey,
                                 secretIdKey?.sign(params.token)
                             )
                         )

src/commonMain/kotlin/net/sergeych/kiloparsec/KiloServerConnection.kt

@@ -60,14 +60,9 @@ class KiloServerConnection<S>(
                     this@KiloServerConnection
                 )
 
-                var public: SigningKey.Public? = null
-                var signature: UByteArray? = null
-                if( serverSigningKey != null ) {
-                    public = serverSigningKey.verifying
-                    signature = serverSigningKey.sign(params!!.token)
-                }
-                Handshake(1u, pair.publicKey, public, signature)
+                Handshake(1u, pair.publicKey, serverSigningKey?.seal(params!!.token))
             }
+
             on(L0ClientId) {
                 var p = params ?: throw RemoteInterface.ClosedException("wrong handshake sequence")
                 val ci = unpack<ClientIdentity>(p.decrypt(it))

src/commonMain/kotlin/net/sergeych/kiloparsec/commands.kt

@@ -1,13 +1,13 @@
 package net.sergeych.kiloparsec
 
 import kotlinx.serialization.Serializable
+import net.sergeych.crypto2.Seal
 import net.sergeych.crypto2.SigningKey
 
 // L0 commands - key exchange and check:
 @Serializable
 data class Handshake(val version: UInt, val publicKey: UByteArray,
-                     val serverPublicKey: SigningKey.Public? = null,
-                     val signature: UByteArray? = null)
+                     val signature: Seal? = null)
 
 @Serializable
 data class ClientIdentity(val clientIdKey: SigningKey.Public?, val signature: UByteArray?)