From fc6a4042f7fca1828f0b8e267cfd660e6fe1d40a Mon Sep 17 00:00:00 2001
From: CGantert345 <57003061+CGantert345@users.noreply.github.com>
Date: Tue, 22 Nov 2022 14:04:27 +0100
Subject: support for SSB barcodes

SSB frame implenmentation including decoding, encoding, signing and verification
---
 .../java/org/uic/barcode/utils/SecurityUtils.java  | 81 ++++++++++++++++++++++
 1 file changed, 81 insertions(+)

(limited to 'src/main/java/org/uic/barcode/utils')

diff --git a/src/main/java/org/uic/barcode/utils/SecurityUtils.java b/src/main/java/org/uic/barcode/utils/SecurityUtils.java
index 5fdbda7..29a2346 100644
--- a/src/main/java/org/uic/barcode/utils/SecurityUtils.java
+++ b/src/main/java/org/uic/barcode/utils/SecurityUtils.java
@@ -1,5 +1,8 @@
 package org.uic.barcode.utils;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.math.BigInteger;
 import java.security.KeyFactory;
 import java.security.NoSuchAlgorithmException;
 import java.security.PrivateKey;
@@ -10,6 +13,7 @@ import java.security.Security;
 import java.security.spec.InvalidKeySpecException;
 import java.security.spec.PKCS8EncodedKeySpec;
 import java.security.spec.X509EncodedKeySpec;
+import java.util.Arrays;
 
 /**
  * The Class SecurityUtils.
@@ -182,4 +186,81 @@ public class SecurityUtils {
 		
 		return null;
 	}
+	
+	/**
+	 * Decode signature integer sequence.
+	 * 
+	 * Support function to decode a DSA signature
+	 * Provides the two DSA signature parameter encoded in a DSA signature
+	 *
+	 * @param bytes the bytes
+	 * @return the big integer[]
+	 * @throws Exception the exception
+	 */
+	public static BigInteger[] decodeSignatureIntegerSequence(byte[] bytes) throws Exception {
+
+		int sequenceTag = (int) bytes[0];
+		
+		if (sequenceTag != 48) throw new Exception("signature is not a sequence");
+		
+		int sequenceLength = (int) bytes[1];
+		
+		if (sequenceLength < 6) throw new Exception("signature sequence too short");
+		
+		BigInteger[] result = new BigInteger[2];
+		
+		int offset = 2;
+		int i = 0;
+		while (offset < bytes.length && i < 2) {
+			int integerTag = (int) bytes[offset];
+			if (integerTag != 2) throw new Exception("signature is not an integer sequence");
+			int integerLength = (int) bytes[offset + 1];
+			byte[] value = Arrays.copyOfRange(bytes, offset + 2, offset + 2 + integerLength);		
+			result[i] = new BigInteger(+1, value);
+			offset = offset + integerLength + 2;
+			i++;
+		}
+
+		return result;
+	}
+	
+	/**
+	 * Encode signature integer sequence.
+	 *  
+	 *  Support function to format two parameters as DER encoded integer list 
+	 *  to get a valid formated DSA signature from the signature parameter
+	 *
+	 * @param i1 the i 1
+	 * @param i2 the i 2
+	 * @return the byte[]
+	 * @throws IOException Signals that an I/O exception has occurred.
+	 */
+	public static byte[] encodeSignatureIntegerSequence(BigInteger i1, BigInteger i2) throws IOException {
+		
+		//SEQUENCE OF --> tag 16
+		int sequenceTag = 16 + 32;  // (bits 6 = 1 constructed)
+		//INTEGER     --> tag 2
+		int integerTag = 2;
+			
+		byte[] b1 = i1.toByteArray();
+        int lb1 = b1.length;
+		byte[] b2 = i2.toByteArray();
+        int lb2 = b2.length;		
+        
+        int sequenceLength = lb1 + lb2 + 4;
+		
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		
+		out.write((byte) sequenceTag);
+		out.write((byte) sequenceLength);   
+		out.write((byte) integerTag);  
+		out.write((byte) lb1);  
+		out.write(b1);   
+		out.write((byte) integerTag);  
+		out.write((byte) lb2);  
+		out.write(b2);   
+
+		return out.toByteArray();
+	}
+
 }
-- 
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