1 files changed, 66 insertions, 0 deletions
diff --git a/crypto/src/asn1/cms/GcmParameters.cs b/crypto/src/asn1/cms/GcmParameters.cs
new file mode 100644
index 000000000..bc86d27fa
--- /dev/null
+++ b/crypto/src/asn1/cms/GcmParameters.cs
@@ -0,0 +1,66 @@
+using System;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Asn1.Cms
+{
+    public class GcmParameters
+        : Asn1Encodable
+    {
+        private const int DefaultIcvLen = 12;
+
+        private readonly byte[] m_nonce;
+        private readonly int m_icvLen;
+
+        public static GcmParameters GetInstance(object obj)
+        {
+            if (obj == null)
+                return null;
+            if (obj is GcmParameters gcmParameters)
+                return gcmParameters;
+            return new GcmParameters(Asn1Sequence.GetInstance(obj));
+        }
+
+        public static GcmParameters GetInstance(Asn1TaggedObject taggedObject, bool declaredExplicit)
+        {
+            return GetInstance(Asn1Sequence.GetInstance(taggedObject, declaredExplicit));
+        }
+
+        private GcmParameters(Asn1Sequence seq)
+        {
+            int count = seq.Count;
+            if (count < 1 || count > 2)
+                throw new ArgumentException("Bad sequence size: " + count, nameof(seq));
+
+            m_nonce = Asn1OctetString.GetInstance(seq[0]).GetOctets();
+
+            if (count > 1)
+            {
+                m_icvLen = DerInteger.GetInstance(seq[1]).IntValueExact;
+            }
+            else
+            {
+                m_icvLen = DefaultIcvLen;
+            }
+        }
+
+        public GcmParameters(byte[] nonce, int icvLen)
+        {
+            m_nonce = Arrays.Clone(nonce);
+            m_icvLen = icvLen;
+        }
+
+        public byte[] GetNonce() => Arrays.Clone(m_nonce);
+
+        public int IcvLen => m_icvLen;
+
+        public override Asn1Object ToAsn1Object()
+        {
+            var nonce = new DerOctetString(m_nonce);
+
+            return m_icvLen == DefaultIcvLen
+                ?   new DerSequence(nonce)
+                :   new DerSequence(nonce, new DerInteger(m_icvLen));
+        }
+    }
+}