diff --git a/implementations/caching/cache/Cache.h b/implementations/caching/cache/Cache.h
index 22408482..0c06b73c 100644
--- a/implementations/caching/cache/Cache.h
+++ b/implementations/caching/cache/Cache.h
@@ -17,6 +17,7 @@ namespace caching {
 template<class Key, class Value, uint32_t MAX_ENTRIES>
 class Cache {
 public:
+  //TODO Current MAX_LIFETIME_SEC only considers time since the element was last pushed to the Cache. Also insert a real MAX_LIFETIME_SEC that forces resync of entries that have been pushed/popped often (e.g. the root blob)
   //TODO Experiment with good values
   static constexpr double PURGE_LIFETIME_SEC = 0.5; //When an entry has this age, it will be purged from the cache
   static constexpr double PURGE_INTERVAL = 0.5; // With this interval, we check for entries to purge
diff --git a/implementations/caching/cache/QueueMap.h b/implementations/caching/cache/QueueMap.h
index e3575cfd..4851c192 100644
--- a/implementations/caching/cache/QueueMap.h
+++ b/implementations/caching/cache/QueueMap.h
@@ -12,6 +12,11 @@
 namespace blockstore {
 namespace caching {
 
+//TODO FreeList for performance
+//TODO Single linked list with pointer to last element (for insertion) should be enough for a queue. No double linked list needed.
+//     But then, popping arbitrary elements needs to be rewritten so that _removeFromQueue() is _removeSuccessorFromQueue()
+//     and the map doesn't store the element itself, but its predecessor. That is, popping might be a bit slower. Test with experiments!
+
 // A class that is a queue and a map at the same time. We could also see it as an addressable queue.
 template<class Key, class Value>
 class QueueMap {
diff --git a/implementations/encrypted/ciphers/CFB_Cipher.h b/implementations/encrypted/ciphers/CFB_Cipher.h
index 4189c282..470004d1 100644
--- a/implementations/encrypted/ciphers/CFB_Cipher.h
+++ b/implementations/encrypted/ciphers/CFB_Cipher.h
@@ -4,6 +4,7 @@
 
 #include <messmer/cpp-utils/data/FixedSizeData.h>
 #include <messmer/cpp-utils/data/Data.h>
+#include <messmer/cpp-utils/random/Random.h>
 #include <boost/optional.hpp>
 #include <cryptopp/cryptopp/modes.h>
 #include "Cipher.h"
@@ -18,6 +19,15 @@ public:
 
   using EncryptionKey = cpputils::FixedSizeData<KeySize>;
 
+  static EncryptionKey CreateKey() {
+    return cpputils::Random::OSRandom().getFixedSize<EncryptionKey::BINARY_LENGTH>();
+  }
+
+  // Used in test cases for fast key creation
+  static EncryptionKey CreatePseudoRandomKey() {
+    return cpputils::Random::PseudoRandom().getFixedSize<EncryptionKey::BINARY_LENGTH>();
+  }
+
   static constexpr unsigned int ciphertextSize(unsigned int plaintextBlockSize) {
     return plaintextBlockSize + IV_SIZE;
   }
@@ -35,7 +45,7 @@ private:
 
 template<typename BlockCipher, unsigned int KeySize>
 cpputils::Data CFB_Cipher<BlockCipher, KeySize>::encrypt(const byte *plaintext, unsigned int plaintextSize, const EncryptionKey &encKey) {
-  auto iv = cpputils::FixedSizeData<IV_SIZE>::CreatePseudoRandom();
+  cpputils::FixedSizeData<IV_SIZE> iv = cpputils::Random::PseudoRandom().getFixedSize<IV_SIZE>();
   auto encryption = typename CryptoPP::CFB_Mode<BlockCipher>::Encryption(encKey.data(), encKey.BINARY_LENGTH, iv.data());
   cpputils::Data ciphertext(ciphertextSize(plaintextSize));
   std::memcpy(ciphertext.data(), iv.data(), IV_SIZE);
diff --git a/implementations/encrypted/ciphers/Cipher.h b/implementations/encrypted/ciphers/Cipher.h
index 65ec3554..3a3ec9e1 100644
--- a/implementations/encrypted/ciphers/Cipher.h
+++ b/implementations/encrypted/ciphers/Cipher.h
@@ -15,9 +15,10 @@ public:
   BOOST_CONCEPT_USAGE(CipherConcept) {
     same_type(UINT32_C(0), X::ciphertextSize(UINT32_C(5)));
     same_type(UINT32_C(0), X::plaintextSize(UINT32_C(5)));
-    typename X::EncryptionKey key = X::EncryptionKey::CreateOSRandom();
-    same_type(cpputils::Data(0), X::encrypt((uint8_t*)nullptr, UINT32_C(0), key));
-    same_type(boost::optional<cpputils::Data>(cpputils::Data(0)), X::decrypt((uint8_t*)nullptr, UINT32_C(0), key));
+    typename X::EncryptionKey key1 = X::CreateKey();
+    typename X::EncryptionKey key2 = X::CreatePseudoRandomKey();
+    same_type(cpputils::Data(0), X::encrypt((uint8_t*)nullptr, UINT32_C(0), key1));
+    same_type(boost::optional<cpputils::Data>(cpputils::Data(0)), X::decrypt((uint8_t*)nullptr, UINT32_C(0), key2));
   }
 
 private:
diff --git a/implementations/encrypted/ciphers/GCM_Cipher.h b/implementations/encrypted/ciphers/GCM_Cipher.h
index 3bc7418c..cd5b0b1e 100644
--- a/implementations/encrypted/ciphers/GCM_Cipher.h
+++ b/implementations/encrypted/ciphers/GCM_Cipher.h
@@ -4,6 +4,7 @@
 
 #include <messmer/cpp-utils/data/FixedSizeData.h>
 #include <messmer/cpp-utils/data/Data.h>
+#include <messmer/cpp-utils/random/Random.h>
 #include <cryptopp/cryptopp/gcm.h>
 #include "Cipher.h"
 
@@ -17,6 +18,15 @@ public:
 
     using EncryptionKey = cpputils::FixedSizeData<KeySize>;
 
+    static EncryptionKey CreateKey() {
+        return cpputils::Random::OSRandom().getFixedSize<EncryptionKey::BINARY_LENGTH>();
+    }
+
+    // Used in test cases for fast key creation
+    static EncryptionKey CreatePseudoRandomKey() {
+        return cpputils::Random::PseudoRandom().getFixedSize<EncryptionKey::BINARY_LENGTH>();
+    }
+
     static constexpr unsigned int ciphertextSize(unsigned int plaintextBlockSize) {
         return plaintextBlockSize + IV_SIZE + TAG_SIZE;
     }
@@ -35,7 +45,7 @@ private:
 
 template<typename BlockCipher, unsigned int KeySize>
 cpputils::Data GCM_Cipher<BlockCipher, KeySize>::encrypt(const byte *plaintext, unsigned int plaintextSize, const EncryptionKey &encKey) {
-    auto iv = cpputils::FixedSizeData<IV_SIZE>::CreatePseudoRandom();
+    cpputils::FixedSizeData<IV_SIZE> iv = cpputils::Random::PseudoRandom().getFixedSize<IV_SIZE>();
     typename CryptoPP::GCM<BlockCipher, CryptoPP::GCM_64K_Tables>::Encryption encryption;
     encryption.SetKeyWithIV(encKey.data(), encKey.BINARY_LENGTH, iv.data(), IV_SIZE);
     cpputils::Data ciphertext(ciphertextSize(plaintextSize));
diff --git a/interface/helpers/BlockStoreWithRandomKeys.h b/interface/helpers/BlockStoreWithRandomKeys.h
index a90edbce..9230cabd 100644
--- a/interface/helpers/BlockStoreWithRandomKeys.h
+++ b/interface/helpers/BlockStoreWithRandomKeys.h
@@ -4,6 +4,7 @@
 
 #include "../BlockStore.h"
 #include "../Block.h"
+#include <messmer/cpp-utils/random/Random.h>
 
 namespace blockstore {
 
@@ -13,7 +14,7 @@ namespace blockstore {
 class BlockStoreWithRandomKeys: public BlockStore {
 public:
   Key createKey() final {
-    return Key::CreatePseudoRandom();
+    return cpputils::Random::PseudoRandom().getFixedSize<Key::BINARY_LENGTH>();
   }
 };
 
diff --git a/test/implementations/encrypted/testutils/FakeAuthenticatedCipher.h b/test/implementations/encrypted/testutils/FakeAuthenticatedCipher.h
index 6ece03d9..73519029 100644
--- a/test/implementations/encrypted/testutils/FakeAuthenticatedCipher.h
+++ b/test/implementations/encrypted/testutils/FakeAuthenticatedCipher.h
@@ -6,9 +6,6 @@
 #include <messmer/cpp-utils/data/FixedSizeData.h>
 
 struct FakeKey {
-  static FakeKey CreateOSRandom() {
-    return FakeKey{(uint8_t)rand()};
-  }
   static FakeKey FromBinary(const void *data) {
     return FakeKey{*(uint8_t*)data};
   }
@@ -24,6 +21,14 @@ public:
 
   using EncryptionKey = FakeKey;
 
+  static EncryptionKey CreateKey() {
+    return FakeKey{(uint8_t)rand()};
+  }
+
+  static EncryptionKey CreatePseudoRandomKey() {
+    return FakeKey{(uint8_t)rand()};
+  }
+
   static EncryptionKey Key1() {
     return FakeKey{5};
   }
diff --git a/test/interface/helpers/BlockStoreWithRandomKeysTest.cpp b/test/interface/helpers/BlockStoreWithRandomKeysTest.cpp
index b88a5add..b503931e 100644
--- a/test/interface/helpers/BlockStoreWithRandomKeysTest.cpp
+++ b/test/interface/helpers/BlockStoreWithRandomKeysTest.cpp
@@ -34,7 +34,7 @@ public:
 
 class BlockMock: public Block {
 public:
-  BlockMock(): Block(Key::CreatePseudoRandom()) {}
+  BlockMock(): Block(cpputils::Random::PseudoRandom().getFixedSize<Key::BINARY_LENGTH>()) {}
   MOCK_CONST_METHOD0(data, const void*());
   MOCK_METHOD3(write, void(const void*, uint64_t, uint64_t));
   MOCK_METHOD0(flush, void());
diff --git a/utils/Key.h b/utils/Key.h
index 17270d12..c395d2ec 100644
--- a/utils/Key.h
+++ b/utils/Key.h
@@ -7,9 +7,9 @@
 
 namespace blockstore {
 
-// A key here is NOT a key for encryption, but a key as used in key->value mappings ("access handle for a block").
-using Key = cpputils::FixedSizeData<16>;
-
+  // A key here is NOT a key for encryption, but a key as used in key->value mappings ("access handle for a block").
+  //TODO Rename to BlockId/BlobId and make it a class containing a FixedSizeData<> member
+  using Key = cpputils::FixedSizeData<16>;
 }
 
 namespace std {