diff --git a/core/java/src/net/i2p/crypto/SHA256Generator.java b/core/java/src/net/i2p/crypto/SHA256Generator.java
index 8d5b6957b..87955646b 100644
--- a/core/java/src/net/i2p/crypto/SHA256Generator.java
+++ b/core/java/src/net/i2p/crypto/SHA256Generator.java
@@ -23,13 +23,18 @@ public final class SHA256Generator {
         return I2PAppContext.getGlobalContext().sha();
     }
     
-    /** Calculate the SHA-256 has of the source
+    /**
+     * Calculate the SHA-256 hash of the source and cache the result.
      * @param source what to hash
      * @return hash of the source
      */
     public final Hash calculateHash(byte[] source) {
         return calculateHash(source, 0, source.length);
     }
+
+    /**
+     * Calculate the hash and cache the result.
+     */
     public final Hash calculateHash(byte[] source, int start, int len) {
         Sha256Standalone digest = acquireGnu();
         digest.update(source, start, len);
@@ -39,6 +44,10 @@ public final class SHA256Generator {
         return Hash.create(rv);
     }
     
+    /**
+     * Use this if you only need the data, not a Hash object.
+     * Does not cache.
+     */
     public final void calculateHash(byte[] source, int start, int len, byte out[], int outOffset) {
         Sha256Standalone digest = acquireGnu();
         digest.update(source, start, len);
diff --git a/router/java/src/net/i2p/data/i2np/I2NPMessageImpl.java b/router/java/src/net/i2p/data/i2np/I2NPMessageImpl.java
index 6b4ab71f4..babf99dae 100644
--- a/router/java/src/net/i2p/data/i2np/I2NPMessageImpl.java
+++ b/router/java/src/net/i2p/data/i2np/I2NPMessageImpl.java
@@ -20,6 +20,7 @@ import net.i2p.data.DataHelper;
 import net.i2p.data.DataStructureImpl;
 import net.i2p.data.Hash;
 import net.i2p.util.Log;
+import net.i2p.util.SimpleByteCache;
 
 /**
  * Defines the base message implementation.
@@ -72,6 +73,7 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
      *  Read the header, then read the rest into buffer, then call
      *  readMessage in the implemented message type
      *
+     *<pre>
      *  Specifically:
      *    1 byte type (if caller didn't read already, as specified by the type param
      *    4 byte ID
@@ -79,9 +81,11 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
      *    2 byte size
      *    1 byte checksum
      *    size bytes of payload (read by readMessage() in implementation)
+     *</pre>
      *
      *  @param type the message type or -1 if we should read it here
      *  @param buffer temp buffer to use
+     *  @return total length of the message
      */
     public int readBytes(InputStream in, int type, byte buffer[]) throws I2NPMessageException, IOException {
         try {
@@ -110,9 +114,11 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
                 cur += numRead;
             }
             
-            Hash calc = _context.sha().calculateHash(buffer, 0, size);
+            byte[] calc = SimpleByteCache.acquire(Hash.HASH_LENGTH);
+            _context.sha().calculateHash(buffer, 0, size, calc, 0);
             //boolean eq = calc.equals(h);
-            boolean eq = DataHelper.eq(checksum, 0, calc.getData(), 0, CHECKSUM_LENGTH);
+            boolean eq = DataHelper.eq(checksum, 0, calc, 0, CHECKSUM_LENGTH);
+            SimpleByteCache.release(calc);
             if (!eq)
                 throw new I2NPMessageException("Hash does not match for " + getClass().getName());
 
@@ -123,11 +129,29 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
             //long time = _context.clock().now() - start;
             //if (time > 50)
             //    _context.statManager().addRateData("i2np.readTime", time, time);
-            return size + Hash.HASH_LENGTH + 1 + 4 + DataHelper.DATE_LENGTH;
+            return CHECKSUM_LENGTH + 1 + 2 + 4 + DataHelper.DATE_LENGTH + size;
         } catch (DataFormatException dfe) {
             throw new I2NPMessageException("Error reading the message header", dfe);
         }
     }
+
+    /**
+     *  Read the header, then read the rest into buffer, then call
+     *  readMessage in the implemented message type
+     *
+     *<pre>
+     *  Specifically:
+     *    1 byte type (if caller didn't read already, as specified by the type param
+     *    4 byte ID
+     *    8 byte expiration
+     *    2 byte size
+     *    1 byte checksum
+     *    size bytes of payload (read by readMessage() in implementation)
+     *</pre>
+     *
+     *  @param type the message type or -1 if we should read it here
+     *  @return total length of the message
+     */
     public int readBytes(byte data[], int type, int offset) throws I2NPMessageException, IOException {
         int cur = offset;
         if (type < 0) {
@@ -153,9 +177,10 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
                                            + " cur=" + cur 
                                            + " wanted=" + size + "]: " + getClass().getName());
 
-        Hash calc = _context.sha().calculateHash(data, cur, size);
-        //boolean eq = calc.equals(h);
-        boolean eq = DataHelper.eq(hdata, 0, calc.getData(), 0, CHECKSUM_LENGTH);
+        byte[] calc = SimpleByteCache.acquire(Hash.HASH_LENGTH);
+        _context.sha().calculateHash(data, cur, size, calc, 0);
+        boolean eq = DataHelper.eq(hdata, 0, calc, 0, CHECKSUM_LENGTH);
+        SimpleByteCache.release(calc);
         if (!eq)
             throw new I2NPMessageException("Hash does not match for " + getClass().getName());
 
@@ -231,7 +256,8 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
         try {
             int writtenLen = writeMessageBody(buffer, prefixLen);
             int payloadLen = writtenLen - prefixLen;
-            Hash h = _context.sha().calculateHash(buffer, prefixLen, payloadLen);
+            byte[] h = SimpleByteCache.acquire(Hash.HASH_LENGTH);
+            _context.sha().calculateHash(buffer, prefixLen, payloadLen, h, 0);
 
             int off = 0;
             DataHelper.toLong(buffer, off, 1, getType());
@@ -242,7 +268,8 @@ public abstract class I2NPMessageImpl extends DataStructureImpl implements I2NPM
             off += DataHelper.DATE_LENGTH;
             DataHelper.toLong(buffer, off, 2, payloadLen);
             off += 2;
-            System.arraycopy(h.getData(), 0, buffer, off, CHECKSUM_LENGTH);
+            System.arraycopy(h, 0, buffer, off, CHECKSUM_LENGTH);
+            SimpleByteCache.release(h);
 
             //long time = _context.clock().now() - start;
             //if (time > 50)
diff --git a/router/java/src/net/i2p/router/tunnel/FragmentHandler.java b/router/java/src/net/i2p/router/tunnel/FragmentHandler.java
index 7948c5387..b21ecc48c 100644
--- a/router/java/src/net/i2p/router/tunnel/FragmentHandler.java
+++ b/router/java/src/net/i2p/router/tunnel/FragmentHandler.java
@@ -15,6 +15,7 @@ import net.i2p.data.i2np.I2NPMessageHandler;
 import net.i2p.router.RouterContext;
 import net.i2p.util.ByteCache;
 import net.i2p.util.Log;
+import net.i2p.util.SimpleByteCache;
 import net.i2p.util.SimpleTimer;
 
 /**
@@ -241,19 +242,21 @@ public class FragmentHandler {
         if (_log.shouldLog(Log.DEBUG))
             _log.debug("endpoint IV: " + Base64.encode(preV, validLength - HopProcessor.IV_LENGTH, HopProcessor.IV_LENGTH));
         
-        Hash v = _context.sha().calculateHash(preV, 0, validLength);
+        byte[] v = SimpleByteCache.acquire(Hash.HASH_LENGTH);
+        _context.sha().calculateHash(preV, 0, validLength, v, 0);
         _validateCache.release(ba);
         
-        boolean eq = DataHelper.eq(v.getData(), 0, preprocessed, offset + HopProcessor.IV_LENGTH, 4);
+        boolean eq = DataHelper.eq(v, 0, preprocessed, offset + HopProcessor.IV_LENGTH, 4);
         if (!eq) {
             if (_log.shouldLog(Log.WARN)) {
                 _log.warn("Corrupt tunnel message - verification fails: " + Base64.encode(preprocessed, offset+HopProcessor.IV_LENGTH, 4)
-                           + " != " + Base64.encode(v.getData(), 0, 4));
+                           + " != " + Base64.encode(v, 0, 4));
                 _log.warn("No matching endpoint: # pad bytes: " + (paddingEnd-(HopProcessor.IV_LENGTH+4)-1)
                            + " offset=" + offset + " length=" + length + " paddingEnd=" + paddingEnd + ' '
                            + Base64.encode(preprocessed, offset, length), new Exception("trace"));
             }
         }
+        SimpleByteCache.release(v);
         
         if (eq) {
             int excessPadding = paddingEnd - (HopProcessor.IV_LENGTH + 4 + 1);