Allow passing version number to key generator

pgpainless-core/src/main/kotlin/org/pgpainless/PGPainless.kt

@@ -10,6 +10,7 @@ import org.bouncycastle.openpgp.PGPKeyRing
 import org.bouncycastle.openpgp.PGPPublicKeyRing
 import org.bouncycastle.openpgp.PGPSecretKeyRing
 import org.bouncycastle.openpgp.PGPSignature
+import org.pgpainless.algorithm.OpenPGPKeyVersion
 import org.pgpainless.decryption_verification.DecryptionBuilder
 import org.pgpainless.encryption_signing.EncryptionBuilder
 import org.pgpainless.key.certification.CertifyCertificate
@@ -31,14 +32,20 @@ class PGPainless private constructor() {
          *
          * @return templates
          */
-        @JvmStatic fun generateKeyRing() = KeyRingTemplates()
+        @JvmStatic
+        @JvmOverloads
+        fun generateKeyRing(version: OpenPGPKeyVersion = OpenPGPKeyVersion.v4) =
+            KeyRingTemplates(version)
 
         /**
          * Build a custom OpenPGP key ring.
          *
          * @return builder
          */
-        @JvmStatic fun buildKeyRing() = KeyRingBuilder()
+        @JvmStatic
+        @JvmOverloads
+        fun buildKeyRing(version: OpenPGPKeyVersion = OpenPGPKeyVersion.v4) =
+            KeyRingBuilder(version)
 
         /**
          * Read an existing OpenPGP key ring.

pgpainless-core/src/main/kotlin/org/pgpainless/algorithm/OpenPGPKeyVersion.kt

@@ -0,0 +1,6 @@
+package org.pgpainless.algorithm
+
+enum class OpenPGPKeyVersion(val version: Int) {
+    v4(4),
+    v6(6),
+}

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingBuilder.kt

@@ -16,6 +16,7 @@ import org.bouncycastle.openpgp.operator.PGPDigestCalculator
 import org.bouncycastle.util.Strings
 import org.pgpainless.PGPainless
 import org.pgpainless.algorithm.KeyFlag
+import org.pgpainless.algorithm.OpenPGPKeyVersion
 import org.pgpainless.algorithm.SignatureType
 import org.pgpainless.bouncycastle.extensions.unlock
 import org.pgpainless.implementation.ImplementationFactory
@@ -25,7 +26,8 @@ import org.pgpainless.signature.subpackets.SignatureSubpackets
 import org.pgpainless.signature.subpackets.SignatureSubpacketsHelper
 import org.pgpainless.util.Passphrase
 
-class KeyRingBuilder : KeyRingBuilderInterface<KeyRingBuilder> {
+class KeyRingBuilder(private val version: OpenPGPKeyVersion) :
+    KeyRingBuilderInterface<KeyRingBuilder> {
 
     private var primaryKeySpec: KeySpec? = null
     private val subKeySpecs = mutableListOf<KeySpec>()

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingTemplates.kt

@@ -7,6 +7,7 @@ package org.pgpainless.key.generation
 import org.bouncycastle.openpgp.PGPSecretKeyRing
 import org.pgpainless.PGPainless.Companion.buildKeyRing
 import org.pgpainless.algorithm.KeyFlag
+import org.pgpainless.algorithm.OpenPGPKeyVersion
 import org.pgpainless.key.generation.KeySpec.Companion.getBuilder
 import org.pgpainless.key.generation.type.KeyType
 import org.pgpainless.key.generation.type.eddsa_legacy.EdDSALegacyCurve
@@ -14,7 +15,7 @@ import org.pgpainless.key.generation.type.rsa.RsaLength
 import org.pgpainless.key.generation.type.xdh_legacy.XDHLegacySpec
 import org.pgpainless.util.Passphrase
 
-class KeyRingTemplates {
+class KeyRingTemplates(private val version: OpenPGPKeyVersion) {
 
     /**
      * Generate an RSA OpenPGP key consisting of an RSA primary key used for certification, a
@@ -31,7 +32,7 @@ class KeyRingTemplates {
         length: RsaLength,
         passphrase: Passphrase = Passphrase.emptyPassphrase()
     ): PGPSecretKeyRing =
-        buildKeyRing()
+        buildKeyRing(version)
             .apply {
                 setPrimaryKey(getBuilder(KeyType.RSA(length), KeyFlag.CERTIFY_OTHER))
                 addSubkey(getBuilder(KeyType.RSA(length), KeyFlag.SIGN_DATA))
@@ -78,7 +79,7 @@ class KeyRingTemplates {
         length: RsaLength,
         passphrase: Passphrase = Passphrase.emptyPassphrase()
     ): PGPSecretKeyRing =
-        buildKeyRing()
+        buildKeyRing(version)
             .apply {
                 setPrimaryKey(
                     getBuilder(
@@ -125,7 +126,7 @@ class KeyRingTemplates {
         userId: CharSequence?,
         passphrase: Passphrase = Passphrase.emptyPassphrase()
     ): PGPSecretKeyRing =
-        buildKeyRing()
+        buildKeyRing(version)
             .apply {
                 setPrimaryKey(
                     getBuilder(
@@ -175,7 +176,7 @@ class KeyRingTemplates {
         userId: CharSequence?,
         passphrase: Passphrase = Passphrase.emptyPassphrase()
     ): PGPSecretKeyRing =
-        buildKeyRing()
+        buildKeyRing(version)
             .apply {
                 setPrimaryKey(
                     getBuilder(