fix #1 UniversalPrivateKey & UniversalPublicKey

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

@@ -20,6 +20,8 @@ import net.sergeych.crypto2.Container.Companion.createWith
  * - [addRecipients] and various [plus] operators to add recipients
  * - [updateData] to change decrypted content for the same recipient keys
  *
+ * Note that container _is serialized encrypted_.
+ *
  * Some rules:
  *
  * When adding public key recipient, it is faster to use your known [SecretKey], but you
@@ -126,8 +128,9 @@ sealed class Container {
     abstract fun updateData(newPlainData: UByteArray, randomFill: IntRange? = null): Container
 
     /**
-     * Binary encoded version. It is desirable to include [Container] as an object, though,
-     * especially when using custom serialization (Json, Boss, etc), it is serializable.
+     * Binary encoded _encrypted_ version. It is desirable to include [Container] as an object, though,
+     * especially when using custom serialization (Json, Boss, etc.), it is serializable. Note that
+     * serialized data is always encrypted.
      * Still, if you need it in binary form, this is a shortcut. You can use [decode] or call
      * [BipackDecoder.decode] to deserialize the binary form.
      */
@@ -474,6 +477,12 @@ sealed class Container {
         inline fun <reified T> decrypt(cipherData: UByteArray, vararg keys: DecryptingKey): T? =
             decryptAsUBytes(cipherData, *keys)?.let { BipackDecoder.decode<T>(it.asByteArray()) }
 
+        inline fun <reified T> decrypt(cipherData: UByteArray, ring: UniversalRing): T? =
+            decode(cipherData)
+                .decryptWith(ring)?.let {
+                    BipackDecoder.decode<T>(it.asByteArray())
+                }
+
         fun decryptAsUBytes(cipherData: UByteArray, vararg keys: DecryptingKey): UByteArray? =
             decode(cipherData).decryptWith(*keys)
 

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

@@ -6,6 +6,11 @@ enum class KeysmagicNumber(val label: String) {
     defaultSymmetric( "sym"),
     defaultSession( "ssn"),
     defaultVerifying( "ver"),
+
+    defaultSigningSecret( "sig"),
+
+    defaultUniversalPublic( "pub+"),
+    defaultUniversalPrivate( "prv+"),
     ;
 
 }

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

@@ -23,6 +23,8 @@ class SigningSecretKey(
             VerifyingPublicKey(Signature.ed25519SkToPk(keyBytes)).also { cachedPublicKey = it }
     }
 
+    override val magic: KeysmagicNumber = KeysmagicNumber.defaultSigningSecret
+
     override fun sign(message: UByteArray): UByteArray = Signature.detached(message, keyBytes)
 
     override fun seal(message: UByteArray, expiresAt: Instant?): Seal =

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

@@ -8,7 +8,6 @@ sealed class UniversalKey: KeyInstance {
 
     abstract val keyBytes: UByteArray
 
-
     @Transient
     open val magic: KeysmagicNumber = KeysmagicNumber.Unknown
 

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

@@ -0,0 +1,47 @@
+package net.sergeych.crypto2
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.Transient
+
+/**
+ * Combination of private/secret keys suitable for both decryption and signing.
+ *
+ * It contains two cryptographically independent keys to raise security to a maximum.
+ * Any converted keys poses a threat while technically possible so we avoid it.
+ */
+@Serializable
+@SerialName("uprv")
+class UniversalPrivateKey(
+    val signingKey: SigningSecretKey,
+    val decryptingKey: SecretKey
+) : UniversalKey(), DecryptingKey by decryptingKey, SigningKey by signingKey {
+
+    override val keyBytes by lazy { signingKey.keyBytes + decryptingKey.keyBytes }
+
+    @Transient
+    override val magic = KeysmagicNumber.defaultUniversalPrivate
+
+    /**
+     * Important! Private key combines signing and decrypting keys, but uses
+     * it of the decrypting one to be used in keyring.
+     */
+    @Transient
+    override val id: KeyId = decryptingKey.id
+
+    /**
+     * Corresponding public key able to verify amd encrypt data created by this
+     * private key.
+     */
+    val publicKey by lazy {
+        UniversalPublicKey(signingKey.verifyingKey, decryptingKey.publicKey)
+    }
+
+    companion object {
+        /**
+         * Generate 2 new random keys (4 key pairs under the hood) to securely signd and
+         * decrypt data.
+         */
+        fun new() = UniversalPrivateKey(SigningSecretKey.new(), SecretKey.new())
+    }
+}

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

@@ -0,0 +1,34 @@
+package net.sergeych.crypto2
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.Transient
+
+/**
+ * Combination of public keys suitable for both encryption and verification. A counterpart
+ * of the [UniversalPrivateKey], available also as [UniversalPrivateKey.publicKey].
+ *
+ * When using [UniversalRing] and [Container], data encrypted with instances og this class
+ * can be decrypted with rings containing the corresponding [UniversalPrivateKey].
+ */
+@Serializable
+@SerialName("upub")
+class UniversalPublicKey(
+    val verifyingKey: VerifyingPublicKey,
+    val encryptingKey: PublicKey
+): UniversalKey(), VerifyingKey by verifyingKey, EncryptingKey by encryptingKey{
+
+    override val keyBytes by lazy { verifyingKey.keyBytes + encryptingKey.keyBytes }
+
+    @Transient
+    override val magic = KeysmagicNumber.defaultUniversalPublic
+
+    /**
+     * Important! Private key combines signing and decrypting keys, but uses
+     * it of the decrypting one to be used in keyring.
+     */
+    @Transient
+    override val id: KeyId = encryptingKey.id
+
+
+}