Somebody likes to try

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -127,6 +127,7 @@ import org.bouncycastle.cms.RecipientInfoGenerator;
 import org.bouncycastle.cms.SignerInfoGenerator;
 import org.bouncycastle.cms.jcajce.JcaSignerInfoGeneratorBuilder;
 import org.bouncycastle.cms.jcajce.JceCMSContentEncryptorBuilder;
+import org.bouncycastle.cms.jcajce.JceKeyAgreeRecipientInfoGenerator;
 import org.bouncycastle.cms.jcajce.JceKeyTransRecipientInfoGenerator;
 import org.bouncycastle.operator.ContentSigner;
 import org.bouncycastle.operator.DigestCalculatorProvider;
@@ -2832,8 +2833,16 @@ public class FragmentCompose extends FragmentBase {
                 // Encrypt
                 CMSEnvelopedDataGenerator cmsEnvelopedDataGenerator = new CMSEnvelopedDataGenerator();
                 if ("EC".equals(privkey.getAlgorithm())) {
+                    JceKeyAgreeRecipientInfoGenerator gen = new JceKeyAgreeRecipientInfoGenerator(
+                            CMSAlgorithm.ECDH_SHA256KDF,
+                            privkey,
+                            chain[0].getPublicKey(),
+                            CMSAlgorithm.AES128_WRAP);
+                    for (X509Certificate cert : certs)
+                        gen.addRecipient(cert);
+                    cmsEnvelopedDataGenerator.addRecipientInfoGenerator(gen);
                     // https://security.stackexchange.com/a/53960
-                    throw new IllegalArgumentException("ECDSA cannot be used for encryption");
+                    // throw new IllegalArgumentException("ECDSA cannot be used for encryption");
                 } else {
                     for (X509Certificate cert : certs) {
                         RecipientInfoGenerator gen = new JceKeyTransRecipientInfoGenerator(cert);