diff --git a/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1Factory.java b/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1Factory.java
index 2762476..ea4eca8 100644
--- a/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1Factory.java
+++ b/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1Factory.java
@@ -23,8 +23,16 @@
 import org.apache.kerby.asn1.type.Asn1Simple;
 import org.apache.kerby.asn1.type.Asn1Type;
 
+/**
+ * ASN1 type factory
+ */
 public class Asn1Factory {
 
+    /**
+     * Create an ASN1 type with specified tag number
+     * @param tagNo
+     * @return ASN1 type
+     */
     public static Asn1Type create(int tagNo) {
         UniversalTag tagNoEnum = UniversalTag.fromValue(tagNo);
         if (tagNoEnum != UniversalTag.UNKNOWN) {
@@ -33,6 +41,11 @@
         throw new IllegalArgumentException("Unexpected tag " + tagNo);
     }
 
+    /**
+     * Create an ASN1 type with specified tag
+     * @param tagNo
+     * @return ASN1 type
+     */
     public static Asn1Type create(UniversalTag tagNo) {
         if (Asn1Simple.isSimple(tagNo)) {
             return Asn1Simple.createSimple(tagNo);
diff --git a/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1InputBuffer.java b/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1InputBuffer.java
index 934b0c1..985bd7e 100644
--- a/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1InputBuffer.java
+++ b/kerby-asn1/src/main/java/org/apache/kerby/asn1/Asn1InputBuffer.java
@@ -27,23 +27,43 @@
 import java.nio.ByteBuffer;
 
 /**
- * Asn1 decoder
+ * Asn1 decoder. Given an input stream, it validates and parses
+ * according to ASN1 spec, and the resultant object can be read
+ * and read until exhausted.
  */
 public class Asn1InputBuffer {
     private final LimitedByteBuffer limitedBuffer;
 
+    /**
+     * Constructor with bytes.
+     * @param bytes
+     */
     public Asn1InputBuffer(byte[] bytes) {
         this(new LimitedByteBuffer(bytes));
     }
 
+    /**
+     * Constructor with a ByteBuffer.
+     * @param byteBuffer
+     */
     public Asn1InputBuffer(ByteBuffer byteBuffer) {
         this(new LimitedByteBuffer(byteBuffer));
     }
 
+    /**
+     * Constructor with LimitedByteBuffer.
+     * @param limitedByteBuffer
+     */
     public Asn1InputBuffer(LimitedByteBuffer limitedByteBuffer) {
         this.limitedBuffer = limitedByteBuffer;
     }
 
+    /**
+     * Parse and read ASN1 object from the stream. If it's already
+     * exhausted then null will be returned to indicate the end.
+     * @return an ASN1 object if available otherwise null
+     * @throws IOException
+     */
     public Asn1Type read() throws IOException {
         if (! limitedBuffer.available()) {
             return null;
@@ -60,6 +80,11 @@
         return one;
     }
 
+    /**
+     *
+     * @param bytes
+     * @throws IOException
+     */
     public void readBytes(byte[] bytes) throws IOException {
         limitedBuffer.readBytes(bytes);
     }