1 files changed, 22 insertions, 1 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/crypto/params/DSAPublicKeyParameters.java b/bcprov/src/main/java/org/bouncycastle/crypto/params/DSAPublicKeyParameters.java
index c0066568..5786ee36 100644
--- a/bcprov/src/main/java/org/bouncycastle/crypto/params/DSAPublicKeyParameters.java
+++ b/bcprov/src/main/java/org/bouncycastle/crypto/params/DSAPublicKeyParameters.java
@@ -5,6 +5,9 @@ import java.math.BigInteger;
 public class DSAPublicKeyParameters
     extends DSAKeyParameters
 {
+    private static final BigInteger ONE = BigInteger.valueOf(1);
+    private static final BigInteger TWO = BigInteger.valueOf(2);
+
     private BigInteger      y;
 
     public DSAPublicKeyParameters(
@@ -13,9 +16,27 @@ public class DSAPublicKeyParameters
     {
         super(false, params);
 
-        this.y = y;
+        this.y = validate(y, params);
     }   
 
+    private BigInteger validate(BigInteger y, DSAParameters params)
+    {
+        if (params != null)
+        {
+            if (TWO.compareTo(y) <= 0 && params.getP().subtract(TWO).compareTo(y) >= 0
+                && ONE.equals(y.modPow(params.getQ(), params.getP())))
+            {
+                return y;
+            }
+
+            throw new IllegalArgumentException("y value does not appear to be in correct group");
+        }
+        else
+        {
+            return y;         // we can't validate without params, fortunately we can't use the key either...
+        }
+    }
+
     public BigInteger getY()
     {
         return y;