diff --git a/crypto/pool/internal.h b/crypto/pool/internal.h
index b39ee42..f9f4838 100644
--- a/crypto/pool/internal.h
+++ b/crypto/pool/internal.h
@@ -39,6 +39,7 @@
 struct crypto_buffer_pool_st {
   LHASH_OF(CRYPTO_BUFFER) *bufs;
   CRYPTO_MUTEX lock;
+  const uint64_t hash_key[2];
 };
 
 
diff --git a/crypto/pool/pool.c b/crypto/pool/pool.c
index 89bf4c2..e889f52 100644
--- a/crypto/pool/pool.c
+++ b/crypto/pool/pool.c
@@ -19,6 +19,8 @@
 
 #include <openssl/bytestring.h>
 #include <openssl/mem.h>
+#include <openssl/rand.h>
+#include <openssl/siphash.h>
 #include <openssl/thread.h>
 
 #include "../internal.h"
@@ -26,10 +28,13 @@
 
 
 static uint32_t CRYPTO_BUFFER_hash(const CRYPTO_BUFFER *buf) {
-  return OPENSSL_hash32(buf->data, buf->len);
+  return (uint32_t)SIPHASH_24(buf->pool->hash_key, buf->data, buf->len);
 }
 
 static int CRYPTO_BUFFER_cmp(const CRYPTO_BUFFER *a, const CRYPTO_BUFFER *b) {
+  // Only |CRYPTO_BUFFER|s from the same pool have compatible hashes.
+  assert(a->pool != NULL);
+  assert(a->pool == b->pool);
   if (a->len != b->len) {
     return 1;
   }
@@ -50,6 +55,7 @@
   }
 
   CRYPTO_MUTEX_init(&pool->lock);
+  RAND_bytes((uint8_t *)&pool->hash_key, sizeof(pool->hash_key));
 
   return pool;
 }
@@ -84,6 +90,7 @@
     CRYPTO_BUFFER tmp;
     tmp.data = (uint8_t *) data;
     tmp.len = len;
+    tmp.pool = pool;
 
     CRYPTO_MUTEX_lock_read(&pool->lock);
     CRYPTO_BUFFER *duplicate = lh_CRYPTO_BUFFER_retrieve(pool->bufs, &tmp);