added encoding preservation for ML-DSA, ML-KEM, added property for triggering seed only PrivateKeyInfo generation, relates to github #1969.

Author: dghgit

core/src/main/java/org/bouncycastle/pqc/crypto/util/PrivateKeyInfoFactory.java

@@ -53,6 +53,7 @@
 import org.bouncycastle.pqc.legacy.crypto.mceliece.McElieceCCA2PrivateKeyParameters;
 import org.bouncycastle.pqc.legacy.crypto.qtesla.QTESLAPrivateKeyParameters;
 import org.bouncycastle.util.Pack;
+import org.bouncycastle.util.Properties;
 
 /**
  * Factory to create ASN.1 private key info objects from lightweight private keys.
@@ -247,18 +248,17 @@ else if (privateKey instanceof MLKEMPrivateKeyParameters)
             MLKEMPrivateKeyParameters params = (MLKEMPrivateKeyParameters)privateKey;
 
             AlgorithmIdentifier algorithmIdentifier = new AlgorithmIdentifier(Utils.mlkemOidLookup(params.getParameters()));
-                                                  
-            return new PrivateKeyInfo(algorithmIdentifier, getBasicPQCEncoding(params.getSeed(), params.getEncoded()), attributes);
-//            byte[] seed = params.getSeed();
-//
-//            if (seed == null)
-//            {
-//                return new PrivateKeyInfo(algorithmIdentifier, params.getEncoded(), attributes);
-//            }
-//            else
-//            {
-//                return new PrivateKeyInfo(algorithmIdentifier, seed, attributes);
-//            }
+
+            byte[] seed = params.getSeed();
+            if (Properties.isOverrideSet("org.bouncycastle.mlkem.seedOnly"))
+            {
+                if (seed == null)    // very difficult to imagine, but...
+                {
+                    throw new IOException("no seed available");
+                }
+                return new PrivateKeyInfo(algorithmIdentifier, seed, attributes);
+            }
+            return new PrivateKeyInfo(algorithmIdentifier, getBasicPQCEncoding(seed, params.getEncoded()), attributes);
         }
         else if (privateKey instanceof NTRULPRimePrivateKeyParameters)
         {
@@ -297,20 +297,16 @@ else if (privateKey instanceof MLDSAPrivateKeyParameters)
 
             AlgorithmIdentifier algorithmIdentifier = new AlgorithmIdentifier(Utils.mldsaOidLookup(params.getParameters()));
 
+            byte[] seed = params.getSeed();
+            if (Properties.isOverrideSet("org.bouncycastle.mldsa.seedOnly"))
+            {
+                if (seed == null)    // very difficult to imagine, but...
+                {
+                    throw new IOException("no seed available");
+                }
+                return new PrivateKeyInfo(algorithmIdentifier, seed, attributes);
+            }
             return new PrivateKeyInfo(algorithmIdentifier, getBasicPQCEncoding(params.getSeed(), params.getEncoded()), attributes);
-//            byte[] seed = params.getSeed();
-//            if (seed == null)
-//            {
-//                MLDSAPublicKeyParameters pubParams = params.getPublicKeyParameters();
-//
-//                return new PrivateKeyInfo(algorithmIdentifier, params.getEncoded(), attributes, pubParams.getEncoded());
-//            }
-//            else
-//            {
-//                MLDSAPublicKeyParameters pubParams = params.getPublicKeyParameters();
-//
-//                return new PrivateKeyInfo(algorithmIdentifier, seed, attributes, pubParams.getEncoded());
-//            }
         }
         else if (privateKey instanceof DilithiumPrivateKeyParameters)
         {

prov/src/main/java/org/bouncycastle/jcajce/provider/asymmetric/mldsa/BCMLDSAPrivateKey.java

@@ -44,6 +44,7 @@ public BCMLDSAPrivateKey(PrivateKeyInfo keyInfo)
     private void init(PrivateKeyInfo keyInfo)
             throws IOException
     {
+        this.encoding = keyInfo.getEncoded();
         init((MLDSAPrivateKeyParameters)PrivateKeyFactory.createKey(keyInfo), keyInfo.getAttributes());
     }
 

prov/src/main/java/org/bouncycastle/jcajce/provider/asymmetric/mlkem/BCMLKEMPrivateKey.java

@@ -25,6 +25,7 @@ public class BCMLKEMPrivateKey
     private transient MLKEMPrivateKeyParameters params;
     private transient String algorithm;
     private transient ASN1Set attributes;
+    private transient byte[] priorEncoding;
 
     public BCMLKEMPrivateKey(
             MLKEMPrivateKeyParameters params)
@@ -43,6 +44,7 @@ private void init(PrivateKeyInfo keyInfo)
         throws IOException
     {
         this.attributes = keyInfo.getAttributes();
+        this.priorEncoding = keyInfo.getPrivateKey().getOctets();
         this.params = (MLKEMPrivateKeyParameters)PrivateKeyFactory.createKey(keyInfo);
         this.algorithm = Strings.toUpperCase(MLKEMParameterSpec.fromName(params.getParameters().getName()).getName());
     }
@@ -89,6 +91,11 @@ public byte[] getEncoded()
         {
             PrivateKeyInfo pki = PrivateKeyInfoFactory.createPrivateKeyInfo(params, attributes);
 
+            if (priorEncoding != null)
+            {
+                pki = new PrivateKeyInfo(pki.getPrivateKeyAlgorithm(), priorEncoding, attributes);
+            }
+
             return pki.getEncoded();
         }
         catch (IOException e)