4 files changed, 110 insertions, 0 deletions

diff --git a/crypto/src/asn1/Asn1Sequence.cs b/crypto/src/asn1/Asn1Sequence.cs
index 8229bfb1d..83e881728 100644
--- a/crypto/src/asn1/Asn1Sequence.cs
+++ b/crypto/src/asn1/Asn1Sequence.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 
 using Org.BouncyCastle.Utilities;
@@ -76,6 +77,28 @@ namespace Org.BouncyCastle.Asn1
             return (Asn1Sequence)Meta.Instance.GetContextInstance(taggedObject, declaredExplicit);
         }
 
+        internal static Asn1Encodable[] ConcatenateElements(Asn1Sequence[] sequences)
+        {
+            int count = sequences.Length;
+            int totalElements = 0;
+            for (int i = 0; i < count; ++i)
+            {
+                totalElements += sequences[i].Count;
+            }
+
+            Asn1Encodable[] concatElements = new Asn1Encodable[totalElements];
+            int pos = 0;
+            for (int i = 0; i < count; ++i)
+            {
+                Asn1Encodable[] elements = sequences[i].m_elements;
+                Array.Copy(elements, 0, concatElements, pos, elements.Length);
+                pos += elements.Length;
+            }
+
+            Debug.Assert(pos == totalElements);
+            return concatElements;
+        }
+
         internal readonly Asn1Encodable[] m_elements;
 
         protected internal Asn1Sequence()
diff --git a/crypto/src/asn1/BerSequence.cs b/crypto/src/asn1/BerSequence.cs
index 48debe3d7..93c92ab91 100644
--- a/crypto/src/asn1/BerSequence.cs
+++ b/crypto/src/asn1/BerSequence.cs
@@ -7,6 +7,35 @@ namespace Org.BouncyCastle.Asn1
 	{
 		public static new readonly BerSequence Empty = new BerSequence();
 
+        public static new BerSequence Concatenate(params Asn1Sequence[] sequences)
+        {
+            if (sequences == null)
+                return Empty;
+
+            switch (sequences.Length)
+            {
+            case 0:
+                return Empty;
+            case 1:
+                return FromSequence(sequences[0]);
+            default:
+                return FromElements(ConcatenateElements(sequences));
+            }
+        }
+
+        internal static new BerSequence FromElements(Asn1Encodable[] elements)
+        {
+            return elements.Length < 1 ? Empty : new BerSequence(elements, clone: false);
+        }
+
+        public static new BerSequence FromSequence(Asn1Sequence sequence)
+        {
+            if (sequence is BerSequence berSequence)
+                return berSequence;
+
+            return FromElements(sequence.m_elements);
+        }
+
 		public static new BerSequence FromVector(Asn1EncodableVector elementVector)
 		{
             return elementVector.Count < 1 ? Empty : new BerSequence(elementVector);
diff --git a/crypto/src/asn1/DLSequence.cs b/crypto/src/asn1/DLSequence.cs
index ba14a8923..05b634f57 100644
--- a/crypto/src/asn1/DLSequence.cs
+++ b/crypto/src/asn1/DLSequence.cs
@@ -7,6 +7,35 @@ namespace Org.BouncyCastle.Asn1
     {
         public static new readonly DLSequence Empty = new DLSequence();
 
+        public static new DLSequence Concatenate(params Asn1Sequence[] sequences)
+        {
+            if (sequences == null)
+                return Empty;
+
+            switch (sequences.Length)
+            {
+            case 0:
+                return Empty;
+            case 1:
+                return FromSequence(sequences[0]);
+            default:
+                return FromElements(ConcatenateElements(sequences));
+            }
+        }
+
+        internal static new DLSequence FromElements(Asn1Encodable[] elements)
+        {
+            return elements.Length < 1 ? Empty : new DLSequence(elements, clone: false);
+        }
+
+        public static new DLSequence FromSequence(Asn1Sequence sequence)
+        {
+            if (sequence is DLSequence dlSequence)
+                return dlSequence;
+
+            return FromElements(sequence.m_elements);
+        }
+
         public static new DLSequence FromVector(Asn1EncodableVector elementVector)
         {
             return elementVector.Count < 1 ? Empty : new DLSequence(elementVector);
diff --git a/crypto/src/asn1/DerSequence.cs b/crypto/src/asn1/DerSequence.cs
index 74dc415ac..4a4aee434 100644
--- a/crypto/src/asn1/DerSequence.cs
+++ b/crypto/src/asn1/DerSequence.cs
@@ -7,6 +7,35 @@ namespace Org.BouncyCastle.Asn1
 	{
 		public static readonly DerSequence Empty = new DerSequence();
 
+        public static DerSequence Concatenate(params Asn1Sequence[] sequences)
+        {
+            if (sequences == null)
+                return Empty;
+
+            switch (sequences.Length)
+            {
+            case 0:
+                return Empty;
+            case 1:
+                return FromSequence(sequences[0]);
+            default:
+                return FromElements(ConcatenateElements(sequences));
+            }
+        }
+
+        internal static DerSequence FromElements(Asn1Encodable[] elements)
+        {
+            return elements.Length < 1 ? Empty : new DerSequence(elements, clone: false);
+        }
+
+        public static DerSequence FromSequence(Asn1Sequence sequence)
+        {
+            if (sequence is DerSequence derSequence)
+                return derSequence;
+
+            return FromElements(sequence.m_elements);
+        }
+
 		public static DerSequence FromVector(Asn1EncodableVector elementVector)
 		{
             return elementVector.Count < 1 ? Empty : new DerSequence(elementVector);