diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CachingBcPublicKeyDataDecryptorFactory.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CachingBcPublicKeyDataDecryptorFactory.kt
index 9bafa6da..1da0a42d 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CachingBcPublicKeyDataDecryptorFactory.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/CachingBcPublicKeyDataDecryptorFactory.kt
@@ -46,6 +46,7 @@ class CachingBcPublicKeyDataDecryptorFactory(
         return decryptorFactory.createDataDecryptor(p0, p1)
     }
 
+    @Deprecated("Deprecated in Java")
     override fun recoverSessionData(
         keyAlgorithm: Int,
         secKeyData: Array<out ByteArray>,
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/HardwareSecurity.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/HardwareSecurity.kt
index b6e2bd17..27f53bc6 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/HardwareSecurity.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/HardwareSecurity.kt
@@ -102,6 +102,7 @@ class HardwareSecurity {
             return factory.createDataDecryptor(seipd, sessionKey)
         }
 
+        @Deprecated("Deprecated in Java")
         override fun recoverSessionData(
             keyAlgorithm: Int,
             secKeyData: Array<out ByteArray>,
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingBuilder.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingBuilder.kt
index 1c3d7df0..cd703ace 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingBuilder.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/KeyRingBuilder.kt
@@ -191,7 +191,7 @@ class KeyRingBuilder(private val version: OpenPGPKeyVersion, private val api: PG
     private fun addSubKeys(primaryKey: PGPKeyPair, ringGenerator: PGPKeyRingGenerator) {
         for (subKeySpec in subKeySpecs) {
             val subKey = generateKeyPair(subKeySpec, version, api.implementation)
-            var hashedSignatureSubpackets: SignatureSubpackets =
+            val hashedSignatureSubpackets: SignatureSubpackets =
                 SignatureSubpackets.createHashedSubpackets(subKey.publicKey).apply {
                     setKeyFlags(subKeySpec.keyFlags)
                     subKeySpec.preferredHashAlgorithmsOverride?.let {
diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SignatureSubpackets.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SignatureSubpackets.kt
index 2a5ea016..28f9ee82 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SignatureSubpackets.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SignatureSubpackets.kt
@@ -292,15 +292,18 @@ class SignatureSubpackets(
         }
     }
 
+    @Deprecated("Use of this subpacket is discouraged.")
     override fun addRevocationKey(revocationKey: PGPPublicKey): SignatureSubpackets = apply {
         addRevocationKey(true, revocationKey)
     }
 
+    @Deprecated("Use of this subpacket is discouraged.")
     override fun addRevocationKey(
         isCritical: Boolean,
         revocationKey: PGPPublicKey
     ): SignatureSubpackets = apply { addRevocationKey(isCritical, false, revocationKey) }
 
+    @Deprecated("Use of this subpacket is discouraged.")
     override fun addRevocationKey(
         isCritical: Boolean,
         isSensitive: Boolean,
@@ -311,10 +314,12 @@ class SignatureSubpackets(
             RevocationKey(isCritical, clazz, revocationKey.algorithm, revocationKey.fingerprint))
     }
 
+    @Deprecated("Use of this subpacket is discouraged.")
     override fun addRevocationKey(revocationKey: RevocationKey): SignatureSubpackets = apply {
         subpacketsGenerator.addCustomSubpacket(revocationKey)
     }
 
+    @Deprecated("Use of this subpacket is discouraged.")
     override fun clearRevocationKeys(): SignatureSubpackets = apply {
         subpacketsGenerator.removePacketsOfType(SignatureSubpacketTags.REVOCATION_KEY)
     }
@@ -450,15 +455,18 @@ class SignatureSubpackets(
         }
     }
 
+    @Deprecated("Usage of subpacket is discouraged")
     override fun setSignerUserId(userId: CharSequence): SignatureSubpackets = apply {
         setSignerUserId(false, userId)
     }
 
+    @Deprecated("Usage of subpacket is discouraged")
     override fun setSignerUserId(isCritical: Boolean, userId: CharSequence): SignatureSubpackets =
         apply {
             setSignerUserId(SignerUserID(isCritical, userId.toString()))
         }
 
+    @Deprecated("Usage of subpacket is discouraged")
     override fun setSignerUserId(signerUserID: SignerUserID?): SignatureSubpackets = apply {
         subpacketsGenerator.removePacketsOfType(SignatureSubpacketTags.SIGNER_USER_ID)
         signerUserID?.let { subpacketsGenerator.setSignerUserID(it.isCritical, it.rawID) }