MimeKit.Cryptography.MultipartEncrypted.Decrypt C# (CSharp) Method

		public MimeEntity Decrypt (OpenPgpContext ctx, out DigitalSignatureCollection signatures)
		{
			if (ctx == null)
				throw new ArgumentNullException ("ctx");

			var protocol = ContentType.Parameters["protocol"];
			if (string.IsNullOrEmpty (protocol))
				throw new FormatException ();

			protocol = protocol.Trim ().ToLowerInvariant ();
			if (!ctx.Supports (protocol))
				throw new NotSupportedException ();

			if (Count < 2)
				throw new FormatException ();

			var version = this[0] as MimePart;
			if (version == null)
				throw new FormatException ();

			var ctype = version.ContentType;
			var value = string.Format ("{0}/{1}", ctype.MediaType, ctype.MediaSubtype);
			if (value.ToLowerInvariant () != protocol)
				throw new FormatException ();

			var encrypted = this[1] as MimePart;
			if (encrypted == null || encrypted.ContentObject == null)
				throw new FormatException ();

			if (!encrypted.ContentType.IsMimeType ("application", "octet-stream"))
				throw new FormatException ();

			using (var memory = new MemoryBlockStream ()) {
				encrypted.ContentObject.DecodeTo (memory);
				memory.Position = 0;

				return ctx.Decrypt (memory, out signatures);
			}
		}