--- a/server/src/main/java/org/iri_research/renkan/models/AbstractRenkanModel.java	Wed Oct 16 23:26:28 2013 +0200
+++ b/server/src/main/java/org/iri_research/renkan/models/AbstractRenkanModel.java	Mon Oct 21 13:58:20 2013 +0200
@@ -1,82 +1,139 @@
 package org.iri_research.renkan.models;
 
 import java.io.Serializable;
+import java.io.UnsupportedEncodingException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
 
+import javax.crypto.spec.SecretKeySpec;
+
+import org.apache.commons.codec.binary.Hex;
+import org.iri_research.renkan.Constants;
+import org.iri_research.renkan.RenkanException;
 import org.iri_research.renkan.RenkanRuntimeException;
 
+public abstract class AbstractRenkanModel<ID extends Serializable> implements
+        IRenkanModel<ID> {
 
-public abstract class AbstractRenkanModel<ID extends Serializable> implements IRenkanModel<ID> {
-	
-	public AbstractRenkanModel(ID id, String title, String description, String uri, String color) {
-		super();
-		this.id = id;
-		this.title = title;
-		this.description = description;
-		this.uri = uri;
-		this.color = color;
-	}
-	
-	protected AbstractRenkanModel() {		
-	}
+    public AbstractRenkanModel(ID id, String title, String description,
+            String uri, String color) {
+        super();
+        this.id = id;
+        this.title = title;
+        this.description = description;
+        this.uri = uri;
+        this.color = color;
+    }
+
+    protected AbstractRenkanModel() {
+    }
+
+    protected ID id;
+    protected String title;
+    protected String description;
+    protected String uri;
+    protected String color;
+
+    @Override
+    public String getTitle() {
+        return this.title;
+    }
 
-	protected ID id;
-	protected String title;
-	protected String description;
-	protected String uri;
-	protected String color;
-	
-	@Override
-	public String getTitle() {
-		return this.title;
-	}
+    @Override
+    public String getDescription() {
+        return this.description;
+    }
+
+    @Override
+    public String getUri() {
+        return this.uri;
+    }
+
+    @Override
+    public String getColor() {
+        return this.color;
+    }
 
-	@Override
-	public String getDescription() {
-		return this.description;
-	}
+    @Override
+    public ID getId() {
+        return this.id;
+    }
+
+    @Override
+    public void setId(ID id) throws RenkanRuntimeException {
+        if (this.id != null) {
+            throw new RenkanRuntimeException(
+                    "Current id is not null, can not change object id");
+        }
+        this.id = id;
+    }
+
+    @Override
+    public void setTitle(String title) {
+        this.title = title;
+    }
 
-	@Override
-	public String getUri() {
-		return this.uri;
-	}
-	
-	@Override
-	public String getColor() {
-		return this.color;
-	}
-	
-	@Override
-	public ID getId() {
-		return this.id;
-	}
-	
-	@Override
-	public void setId(ID id) throws RenkanRuntimeException {
-		if(this.id != null) {
-			throw new RenkanRuntimeException("Current id is not null, can not change object id");
-		}
-		this.id = id;
-	}
+    @Override
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    @Override
+    public void setUri(String uri) {
+        this.uri = uri;
+    }
+
+    @Override
+    public void setColor(String color) {
+        this.color = color;
+    }
+    
+    abstract protected String getRawKeyPart(); 
+
+    private String getRawKey(String salt) {
+        StringBuffer key = new StringBuffer(salt != null ? salt + "|" : "");
+        key.append(this.getId());
+        key.append('|');
+        key.append(this.getRawKeyPart());
+        return key.toString();
+    }
+
+    public String getKey(String salt) throws RenkanException {
+
+        String rawKey = this.getRawKey(salt);
 
-	@Override
-	public void setTitle(String title) {
-		this.title = title;
-	}
-
-	@Override
-	public void setDescription(String description) {
-		this.description = description;
-	}
+        MessageDigest md;
+        try {
+            md = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RenkanException("NoSuchAlgorithmException digest: "
+                    + e.getMessage(), e);
+        }
+        String key;
+        final SecretKeySpec secret_key = new SecretKeySpec(
+                Constants.KEYHEX.getBytes(), "HmacSHA256");
+        md.update(secret_key.getEncoded());
+        try {
+            key = Hex.encodeHexString(md.digest(rawKey.getBytes("UTF-8")));
+        } catch (UnsupportedEncodingException e) {
+            throw new RenkanException("UnsupportedEncodingException digest: "
+                    + e.getMessage(), e);
+        }
 
-	@Override
-	public void setUri(String uri) {
-		this.uri = uri;
-	}
+        return key;
+    }
+
+    public boolean checkKey(String key, String salt) throws RenkanException {
+
+        if (key == null || key.isEmpty()) {
+            return false;
+        }
 
-	@Override
-	public void setColor(String color) {
-		this.color = color;
-	}
-	
-		
+        String signature = key;
+
+        String new_key = this.getKey(salt);
+
+        return new_key.equals(signature);
+    }
+
 }