diff --git a/src/cpp-utils/CMakeLists.txt b/src/cpp-utils/CMakeLists.txt
index 3985f401..7eb3da79 100644
--- a/src/cpp-utils/CMakeLists.txt
+++ b/src/cpp-utils/CMakeLists.txt
@@ -2,9 +2,9 @@ project (cpp-utils)
 
 set(SOURCES
         crypto/symmetric/ciphers.cpp
-        crypto/kdf/DerivedKey.cpp
         crypto/kdf/Scrypt.cpp
-        crypto/kdf/DerivedKeyConfig.cpp
+        crypto/kdf/SCryptParameters.cpp
+        crypto/kdf/PasswordBasedKDF.cpp
         crypto/RandomPadding.cpp
         process/daemonize.cpp
         process/subprocess.cpp
diff --git a/src/cpp-utils/crypto/kdf/DerivedKey.cpp b/src/cpp-utils/crypto/kdf/DerivedKey.cpp
deleted file mode 100644
index 7968d456..00000000
--- a/src/cpp-utils/crypto/kdf/DerivedKey.cpp
+++ /dev/null
@@ -1 +0,0 @@
-#include "DerivedKey.h"
diff --git a/src/cpp-utils/crypto/kdf/DerivedKey.h b/src/cpp-utils/crypto/kdf/DerivedKey.h
deleted file mode 100644
index 2f6eb582..00000000
--- a/src/cpp-utils/crypto/kdf/DerivedKey.h
+++ /dev/null
@@ -1,39 +0,0 @@
-#pragma once
-#ifndef MESSMER_CPPUTILS_CRYPTO_KDF_DERIVEDKEY_H
-#define MESSMER_CPPUTILS_CRYPTO_KDF_DERIVEDKEY_H
-
-#include "../../data/FixedSizeData.h"
-#include "DerivedKeyConfig.h"
-
-namespace cpputils {
-
-    template<size_t KEY_LENGTH>
-    class DerivedKey final {
-    public:
-        DerivedKey(DerivedKeyConfig config, const FixedSizeData<KEY_LENGTH> &key): _config(std::move(config)), _key(key) {}
-        DerivedKey(DerivedKey &&rhs) = default;
-
-        const DerivedKeyConfig &config() const {
-            return _config;
-        }
-
-        DerivedKeyConfig moveOutConfig() {
-            return std::move(_config);
-        }
-
-        const FixedSizeData<KEY_LENGTH> &key() const {
-            return _key;
-        }
-
-        FixedSizeData<KEY_LENGTH> moveOutKey() {
-            return std::move(_key);
-        }
-    private:
-        DerivedKeyConfig _config;
-        FixedSizeData<KEY_LENGTH> _key;
-
-        DISALLOW_COPY_AND_ASSIGN(DerivedKey);
-    };
-}
-
-#endif
diff --git a/src/cpp-utils/crypto/kdf/DerivedKeyConfig.cpp b/src/cpp-utils/crypto/kdf/DerivedKeyConfig.cpp
deleted file mode 100644
index 5883cf0b..00000000
--- a/src/cpp-utils/crypto/kdf/DerivedKeyConfig.cpp
+++ /dev/null
@@ -1,27 +0,0 @@
-#include "DerivedKeyConfig.h"
-
-using std::istream;
-using std::ostream;
-using boost::optional;
-using boost::none;
-
-namespace cpputils {
-    void DerivedKeyConfig::serialize(Serializer *target) const {
-        target->writeUint64(_N);
-        target->writeUint32(_r);
-        target->writeUint32(_p);
-        target->writeData(_salt);
-    }
-
-    size_t DerivedKeyConfig::serializedSize() const {
-        return Serializer::DataSize(_salt) + sizeof(uint64_t) + sizeof(uint32_t) + sizeof(uint32_t);
-    }
-
-    DerivedKeyConfig DerivedKeyConfig::deserialize(Deserializer *source) {
-        uint64_t N = source->readUint64();
-        uint32_t r = source->readUint32();
-        uint32_t p = source->readUint32();
-        Data salt = source->readData();
-        return DerivedKeyConfig(std::move(salt), N, r, p);
-    }
-}
diff --git a/src/cpp-utils/crypto/kdf/PasswordBasedKDF.cpp b/src/cpp-utils/crypto/kdf/PasswordBasedKDF.cpp
new file mode 100644
index 00000000..b7f5dc25
--- /dev/null
+++ b/src/cpp-utils/crypto/kdf/PasswordBasedKDF.cpp
@@ -0,0 +1 @@
+#include "PasswordBasedKDF.h"
diff --git a/src/cpp-utils/crypto/kdf/PasswordBasedKDF.h b/src/cpp-utils/crypto/kdf/PasswordBasedKDF.h
new file mode 100644
index 00000000..e43f143c
--- /dev/null
+++ b/src/cpp-utils/crypto/kdf/PasswordBasedKDF.h
@@ -0,0 +1,31 @@
+#pragma once
+#ifndef MESSMER_CPPUTILS_CRYPTO_KDF_PASSWORDBASEDKDF_H
+#define MESSMER_CPPUTILS_CRYPTO_KDF_PASSWORDBASEDKDF_H
+
+#include "../../data/FixedSizeData.h"
+#include "../../data/Data.h"
+
+namespace cpputils {
+
+    class PasswordBasedKDF {
+    public:
+        virtual ~PasswordBasedKDF() {}
+
+        template<size_t KEYSIZE> FixedSizeData<KEYSIZE> deriveKey(const std::string &password);
+        virtual const Data &kdfParameters() const = 0;
+
+    protected:
+        virtual void derive(void *destination, size_t size, const std::string &password) = 0;
+    };
+
+    template<size_t KEYSIZE> FixedSizeData<KEYSIZE>
+    inline PasswordBasedKDF::deriveKey(const std::string &password) {
+        auto result = FixedSizeData<KEYSIZE>::Null();
+        derive(result.data(), result.BINARY_LENGTH, password);
+        return result;
+    }
+
+}
+
+
+#endif
diff --git a/src/cpp-utils/crypto/kdf/SCryptParameters.cpp b/src/cpp-utils/crypto/kdf/SCryptParameters.cpp
new file mode 100644
index 00000000..a0099cbf
--- /dev/null
+++ b/src/cpp-utils/crypto/kdf/SCryptParameters.cpp
@@ -0,0 +1,42 @@
+#include "SCryptParameters.h"
+
+using std::istream;
+using std::ostream;
+using boost::optional;
+using boost::none;
+using cpputils::Data;
+
+namespace cpputils {
+    Data SCryptParameters::serialize() const {
+        Serializer serializer(_serializedSize());
+        serializer.writeUint64(_N);
+        serializer.writeUint32(_r);
+        serializer.writeUint32(_p);
+        serializer.writeTailData(_salt);
+        return serializer.finished();
+    }
+
+    size_t SCryptParameters::_serializedSize() const {
+        return _salt.size() + sizeof(uint64_t) + sizeof(uint32_t) + sizeof(uint32_t);
+    }
+
+    SCryptParameters SCryptParameters::deserialize(const cpputils::Data &data) {
+        Deserializer deserializer(&data);
+        uint64_t N = deserializer.readUint64();
+        uint32_t r = deserializer.readUint32();
+        uint32_t p = deserializer.readUint32();
+        Data salt = deserializer.readTailData();
+        deserializer.finished();
+        return SCryptParameters(std::move(salt), N, r, p);
+    }
+
+#ifndef CRYFS_NO_COMPATIBILITY
+    SCryptParameters SCryptParameters::deserializeOldFormat(Deserializer *source) {
+        uint64_t N = source->readUint64();
+        uint32_t r = source->readUint32();
+        uint32_t p = source->readUint32();
+        Data salt = source->readData();
+        return SCryptParameters(std::move(salt), N, r, p);
+    }
+#endif
+}
diff --git a/src/cpp-utils/crypto/kdf/DerivedKeyConfig.h b/src/cpp-utils/crypto/kdf/SCryptParameters.h
similarity index 59%
rename from src/cpp-utils/crypto/kdf/DerivedKeyConfig.h
rename to src/cpp-utils/crypto/kdf/SCryptParameters.h
index 045ed0eb..785fc336 100644
--- a/src/cpp-utils/crypto/kdf/DerivedKeyConfig.h
+++ b/src/cpp-utils/crypto/kdf/SCryptParameters.h
@@ -13,19 +13,19 @@ namespace cpputils {
     //TODO Test operator==/!=
     //TODO Use SCryptSettings as a member here instead of storing _N, _r, _p.
 
-    class DerivedKeyConfig final {
+    class SCryptParameters final {
     public:
-        DerivedKeyConfig(Data salt, uint64_t N, uint32_t r, uint32_t p)
+        SCryptParameters(Data salt, uint64_t N, uint32_t r, uint32_t p)
                 : _salt(std::move(salt)),
                   _N(N), _r(r), _p(p) { }
 
-        DerivedKeyConfig(const DerivedKeyConfig &rhs)
+        SCryptParameters(const SCryptParameters &rhs)
                 :_salt(rhs._salt.copy()),
                  _N(rhs._N), _r(rhs._r), _p(rhs._p) { }
 
-        DerivedKeyConfig(DerivedKeyConfig &&rhs) = default;
+        SCryptParameters(SCryptParameters &&rhs) = default;
 
-        DerivedKeyConfig &operator=(const DerivedKeyConfig &rhs) {
+        SCryptParameters &operator=(const SCryptParameters &rhs) {
             _salt = rhs._salt.copy();
             _N = rhs._N;
             _r = rhs._r;
@@ -33,7 +33,7 @@ namespace cpputils {
             return *this;
         }
 
-        DerivedKeyConfig &operator=(DerivedKeyConfig &&rhs) = default;
+        SCryptParameters &operator=(SCryptParameters &&rhs) = default;
 
         const Data &salt() const {
             return _salt;
@@ -51,24 +51,31 @@ namespace cpputils {
             return _p;
         }
 
-        void serialize(Serializer *destination) const;
+        cpputils::Data serialize() const;
 
-        size_t serializedSize() const;
+        static SCryptParameters deserialize(const cpputils::Data &data);
 
-        static DerivedKeyConfig deserialize(Deserializer *source);
+#ifndef CRYFS_NO_COMPATIBILITY
+        static SCryptParameters deserializeOldFormat(cpputils::Deserializer *deserializer);
+        size_t serializedSize() const {
+            return _serializedSize();
+        }
+#endif
 
     private:
+        size_t _serializedSize() const;
+
         Data _salt;
         uint64_t _N;
         uint32_t _r;
         uint32_t _p;
     };
 
-    inline bool operator==(const DerivedKeyConfig &lhs, const DerivedKeyConfig &rhs) {
+    inline bool operator==(const SCryptParameters &lhs, const SCryptParameters &rhs) {
         return lhs.salt() == rhs.salt() && lhs.N() == rhs.N() && lhs.r() == rhs.r() && lhs.p() == rhs.p();
     }
 
-    inline bool operator!=(const DerivedKeyConfig &lhs, const DerivedKeyConfig &rhs) {
+    inline bool operator!=(const SCryptParameters &lhs, const SCryptParameters &rhs) {
         return !operator==(lhs, rhs);
     }
 
diff --git a/src/cpp-utils/crypto/kdf/Scrypt.cpp b/src/cpp-utils/crypto/kdf/Scrypt.cpp
index edf14e62..5a48ca6a 100644
--- a/src/cpp-utils/crypto/kdf/Scrypt.cpp
+++ b/src/cpp-utils/crypto/kdf/Scrypt.cpp
@@ -1,7 +1,45 @@
 #include "Scrypt.h"
 
+using std::string;
+
 namespace cpputils {
+
     constexpr SCryptSettings SCrypt::ParanoidSettings;
     constexpr SCryptSettings SCrypt::DefaultSettings;
     constexpr SCryptSettings SCrypt::TestSettings;
+
+    unique_ref<SCrypt> SCrypt::forNewKey(const SCryptSettings &settings) {
+        SCryptParameters kdfParameters(Random::PseudoRandom().get(settings.SALT_LEN), settings.N, settings.r, settings.p);
+        return make_unique_ref<SCrypt>(std::move(kdfParameters));
+    }
+
+    unique_ref<SCrypt> SCrypt::forExistingKey(const Data &parameters) {
+        return make_unique_ref<SCrypt>(SCryptParameters::deserialize(parameters));
+    }
+
+    SCrypt::SCrypt(SCryptParameters config)
+            :_config(std::move(config)), _serializedConfig(_config.serialize()), _wasGeneratedBefore(false) {
+    }
+
+    void SCrypt::derive(void *destination, size_t size, const string &password) {
+        _checkCallOnlyOnce();
+        int errorcode = crypto_scrypt(reinterpret_cast<const uint8_t*>(password.c_str()), password.size(),
+                                      reinterpret_cast<const uint8_t*>(_config.salt().data()), _config.salt().size(),
+                                      _config.N(), _config.r(), _config.p(),
+                                      static_cast<uint8_t*>(destination), size);
+        if (errorcode != 0) {
+            throw std::runtime_error("Error running scrypt key derivation.");
+        }
+    }
+
+    const Data &SCrypt::kdfParameters() const {
+        return _serializedConfig;
+    }
+
+    void SCrypt::_checkCallOnlyOnce() {
+        if (_wasGeneratedBefore) {
+            throw std::runtime_error("An SCrypt instance can only generate exactly one key. Generating multiple keys would be insecure because we would use the same salt.");
+        }
+        _wasGeneratedBefore = true;
+    }
 }
\ No newline at end of file
diff --git a/src/cpp-utils/crypto/kdf/Scrypt.h b/src/cpp-utils/crypto/kdf/Scrypt.h
index e7c80192..6578e950 100644
--- a/src/cpp-utils/crypto/kdf/Scrypt.h
+++ b/src/cpp-utils/crypto/kdf/Scrypt.h
@@ -4,11 +4,14 @@
 
 #include "../../macros.h"
 #include "../../random/Random.h"
+#include "../../pointer/unique_ref.h"
+#include "PasswordBasedKDF.h"
+
 extern "C" {
     #include <scrypt/lib/crypto/crypto_scrypt.h>
 }
 #include <stdexcept>
-#include "DerivedKey.h"
+#include "SCryptParameters.h"
 
 namespace cpputils {
 
@@ -19,36 +22,29 @@ namespace cpputils {
         uint32_t p;
     };
 
-    class SCrypt final {
+    class SCrypt final : public PasswordBasedKDF {
     public:
         static constexpr SCryptSettings ParanoidSettings = SCryptSettings {32, 1048576, 8, 16};
         static constexpr SCryptSettings DefaultSettings = SCryptSettings {32, 1048576, 4, 1};
         static constexpr SCryptSettings TestSettings = SCryptSettings {32, 1024, 1, 1};
 
-        SCrypt() {}
+        static unique_ref<SCrypt> forNewKey(const SCryptSettings &settings);
+        static unique_ref<SCrypt> forExistingKey(const Data &parameters);
 
-        template<size_t KEYSIZE>
-        DerivedKey<KEYSIZE> generateKey(const std::string &password, const SCryptSettings &settings) {
-            auto salt = Random::PseudoRandom().get(settings.SALT_LEN);
-            auto config = DerivedKeyConfig(std::move(salt), settings.N, settings.r, settings.p);
-            auto key = generateKeyFromConfig<KEYSIZE>(password, config);
-            return DerivedKey<KEYSIZE>(std::move(config), key);
-        }
+        const Data &kdfParameters() const override;
 
-        template<size_t KEYSIZE>
-        FixedSizeData<KEYSIZE> generateKeyFromConfig(const std::string &password, const DerivedKeyConfig &config) {
-            auto key = FixedSizeData<KEYSIZE>::Null();
-            int errorcode = crypto_scrypt(reinterpret_cast<const uint8_t*>(password.c_str()), password.size(),
-                          reinterpret_cast<const uint8_t*>(config.salt().data()), config.salt().size(),
-                          config.N(), config.r(), config.p(),
-                          static_cast<uint8_t*>(key.data()), KEYSIZE);
-            if (errorcode != 0) {
-                throw std::runtime_error("Error running scrypt key derivation.");
-            }
-            return key;
-        }
+        SCrypt(SCryptParameters config);
+
+    protected:
+        void derive(void *destination, size_t size, const std::string &password) override;
 
     private:
+        void _checkCallOnlyOnce();
+
+        SCryptParameters _config;
+        Data _serializedConfig;
+        bool _wasGeneratedBefore;
+
         DISALLOW_COPY_AND_ASSIGN(SCrypt);
     };
 }
diff --git a/src/cryfs/config/CryConfigFile.cpp b/src/cryfs/config/CryConfigFile.cpp
index 553f6449..2455ac29 100644
--- a/src/cryfs/config/CryConfigFile.cpp
+++ b/src/cryfs/config/CryConfigFile.cpp
@@ -44,7 +44,12 @@ optional<CryConfigFile> CryConfigFile::load(const bf::path &path, const string &
         LOG(ERROR) << "Inner cipher algorithm used to encrypt config file doesn't match config value";
         return none;
     }
-    return CryConfigFile(path, std::move(config), std::move(*encryptor));
+    auto configFile = CryConfigFile(path, std::move(config), std::move(*encryptor));
+    if (decrypted->wasInDeprecatedConfigFormat) {
+        // Migrate it to new format
+        configFile.save();
+    }
+    return configFile;
 }
 
 CryConfigFile CryConfigFile::create(const bf::path &path, CryConfig config, const string &password, const SCryptSettings &scryptSettings) {
diff --git a/src/cryfs/config/crypto/CryConfigEncryptor.cpp b/src/cryfs/config/crypto/CryConfigEncryptor.cpp
index a27b0f03..5c97982f 100644
--- a/src/cryfs/config/crypto/CryConfigEncryptor.cpp
+++ b/src/cryfs/config/crypto/CryConfigEncryptor.cpp
@@ -6,8 +6,6 @@ using cpputils::unique_ref;
 using cpputils::make_unique_ref;
 using cpputils::Data;
 using cpputils::RandomPadding;
-using cpputils::DerivedKeyConfig;
-using cpputils::DerivedKey;
 using cpputils::FixedSizeData;
 using boost::optional;
 using boost::none;
@@ -17,8 +15,8 @@ namespace cryfs {
     constexpr size_t CryConfigEncryptor::OuterKeySize;
     constexpr size_t CryConfigEncryptor::MaxTotalKeySize;
 
-    CryConfigEncryptor::CryConfigEncryptor(DerivedKey<MaxTotalKeySize> derivedKey)
-            : _derivedKey(std::move(derivedKey)) {
+    CryConfigEncryptor::CryConfigEncryptor(FixedSizeData<MaxTotalKeySize> derivedKey, cpputils::Data kdfParameters)
+            : _derivedKey(std::move(derivedKey)), _kdfParameters(std::move(kdfParameters)) {
     }
 
     Data CryConfigEncryptor::encrypt(const Data &plaintext, const string &cipherName) const {
@@ -29,18 +27,6 @@ namespace cryfs {
     }
 
     optional<CryConfigEncryptor::Decrypted> CryConfigEncryptor::decrypt(const Data &data) const {
-        auto innerConfig = _loadInnerConfig(data);
-        if (innerConfig == none) {
-            return none;
-        }
-        auto plaintext = _innerEncryptor(innerConfig->cipherName)->decrypt(*innerConfig);
-        if (plaintext == none) {
-            return none;
-        }
-        return Decrypted{std::move(*plaintext), innerConfig->cipherName};
-    }
-
-    optional<InnerConfig> CryConfigEncryptor::_loadInnerConfig(const Data &data) const {
         auto outerConfig = OuterConfig::deserialize(data);
         if (outerConfig == none) {
             return none;
@@ -49,16 +35,24 @@ namespace cryfs {
         if(serializedInnerConfig == none) {
             return none;
         }
-        return InnerConfig::deserialize(*serializedInnerConfig);
+        auto innerConfig = InnerConfig::deserialize(*serializedInnerConfig);
+        if (innerConfig == none) {
+            return none;
+        }
+        auto plaintext = _innerEncryptor(innerConfig->cipherName)->decrypt(*innerConfig);
+        if (plaintext == none) {
+            return none;
+        }
+        return Decrypted{std::move(*plaintext), innerConfig->cipherName, outerConfig->wasInDeprecatedConfigFormat};
     }
 
     unique_ref<OuterEncryptor> CryConfigEncryptor::_outerEncryptor() const {
-        auto outerKey = _derivedKey.key().take<OuterKeySize>();
-        return make_unique_ref<OuterEncryptor>(outerKey, _derivedKey.config());
+        auto outerKey = _derivedKey.take<OuterKeySize>();
+        return make_unique_ref<OuterEncryptor>(outerKey, _kdfParameters.copy());
     }
 
     unique_ref<InnerEncryptor> CryConfigEncryptor::_innerEncryptor(const string &cipherName) const {
-        auto innerKey = _derivedKey.key().drop<OuterKeySize>();
+        auto innerKey = _derivedKey.drop<OuterKeySize>();
         return CryCiphers::find(cipherName).createInnerConfigEncryptor(innerKey);
     }
 }
diff --git a/src/cryfs/config/crypto/CryConfigEncryptor.h b/src/cryfs/config/crypto/CryConfigEncryptor.h
index cbcfb06f..a206c0da 100644
--- a/src/cryfs/config/crypto/CryConfigEncryptor.h
+++ b/src/cryfs/config/crypto/CryConfigEncryptor.h
@@ -5,8 +5,6 @@
 #include <cpp-utils/pointer/unique_ref.h>
 #include <cpp-utils/data/Deserializer.h>
 #include <cpp-utils/data/Serializer.h>
-#include <cpp-utils/crypto/kdf/DerivedKeyConfig.h>
-#include <cpp-utils/crypto/kdf/DerivedKey.h>
 #include <cpp-utils/crypto/symmetric/ciphers.h>
 #include "inner/InnerEncryptor.h"
 #include "outer/OuterEncryptor.h"
@@ -22,19 +20,20 @@ namespace cryfs {
         struct Decrypted {
             cpputils::Data data;
             std::string cipherName;
+            bool wasInDeprecatedConfigFormat;
         };
 
-        CryConfigEncryptor(cpputils::DerivedKey<MaxTotalKeySize> derivedKey);
+        CryConfigEncryptor(cpputils::FixedSizeData<MaxTotalKeySize> derivedKey, cpputils::Data _kdfParameters);
 
         cpputils::Data encrypt(const cpputils::Data &plaintext, const std::string &cipherName) const;
         boost::optional<Decrypted> decrypt(const cpputils::Data &data) const;
 
     private:
-        boost::optional<InnerConfig> _loadInnerConfig(const cpputils::Data &data) const;
         cpputils::unique_ref<OuterEncryptor> _outerEncryptor() const;
         cpputils::unique_ref<InnerEncryptor> _innerEncryptor(const std::string &cipherName) const;
 
-        cpputils::DerivedKey<MaxTotalKeySize> _derivedKey;
+        cpputils::FixedSizeData<MaxTotalKeySize> _derivedKey;
+        cpputils::Data _kdfParameters;
 
         DISALLOW_COPY_AND_ASSIGN(CryConfigEncryptor);
     };
diff --git a/src/cryfs/config/crypto/CryConfigEncryptorFactory.cpp b/src/cryfs/config/crypto/CryConfigEncryptorFactory.cpp
index 3b33f42f..fe2c39c4 100644
--- a/src/cryfs/config/crypto/CryConfigEncryptorFactory.cpp
+++ b/src/cryfs/config/crypto/CryConfigEncryptorFactory.cpp
@@ -8,8 +8,8 @@ using boost::none;
 using cpputils::unique_ref;
 using cpputils::make_unique_ref;
 using cpputils::Data;
-using cpputils::DerivedKey;
-using cpputils::DerivedKeyConfig;
+using cpputils::FixedSizeData;
+using cpputils::SCryptParameters;
 using cpputils::SCrypt;
 using cpputils::SCryptSettings;
 using std::string;
@@ -22,21 +22,20 @@ namespace cryfs {
         if (outerConfig == none) {
             return none;
         }
-        auto derivedKey = _deriveKey(outerConfig->keyConfig, password);
-        return make_unique_ref<CryConfigEncryptor>(std::move(derivedKey));
-    }
-
-    DerivedKey<CryConfigEncryptor::MaxTotalKeySize>
-    CryConfigEncryptorFactory::_deriveKey(const DerivedKeyConfig &keyConfig, const std::string &password) {
-        //TODO It would be better, not to generate a MaxTotalKeySize key here, but to generate the outer key first, and then
-        //     (once we know which inner cipher was used) only generate as many key bytes as we need for the inner cipher.
-        //     This would need a change in the scrypt interface though, because right now we can't continue past key computations.
-        auto key = SCrypt().generateKeyFromConfig<CryConfigEncryptor::MaxTotalKeySize>(password, keyConfig);
-        return DerivedKey<CryConfigEncryptor::MaxTotalKeySize>(keyConfig, std::move(key));
+        return _deriveKey(SCrypt::forExistingKey(outerConfig->kdfParameters), password);
     }
 
     unique_ref<CryConfigEncryptor> CryConfigEncryptorFactory::deriveKey(const string &password, const SCryptSettings &scryptSettings) {
-        auto derivedKey = cpputils::SCrypt().generateKey<CryConfigEncryptor::MaxTotalKeySize>(password, scryptSettings);
-        return make_unique_ref<CryConfigEncryptor>(std::move(derivedKey));
+        return _deriveKey(SCrypt::forNewKey(scryptSettings), password);
+    }
+
+    unique_ref<CryConfigEncryptor>
+    CryConfigEncryptorFactory::_deriveKey(cpputils::unique_ref<SCrypt> kdf, const string &password) {
+        //TODO It would be better, not to generate a MaxTotalKeySize key here, but to generate the outer key first, and then
+        //     (once we know which inner cipher was used) only generate as many key bytes as we need for the inner cipher.
+        //     This would need a change in the scrypt interface though, because right now we can't continue past key computations.
+        //TODO I might be able to know the actual key size here (at runtime) and switch the SCrypt deriveKey() interface to getting a dynamic size.
+        auto key = kdf->deriveKey<CryConfigEncryptor::MaxTotalKeySize>(password);
+        return make_unique_ref<CryConfigEncryptor>(std::move(key), kdf->kdfParameters().copy());
     }
 }
diff --git a/src/cryfs/config/crypto/CryConfigEncryptorFactory.h b/src/cryfs/config/crypto/CryConfigEncryptorFactory.h
index b76c13ce..312b7491 100644
--- a/src/cryfs/config/crypto/CryConfigEncryptorFactory.h
+++ b/src/cryfs/config/crypto/CryConfigEncryptorFactory.h
@@ -18,8 +18,7 @@ namespace cryfs {
 
     private:
 
-        static cpputils::DerivedKey<CryConfigEncryptor::MaxTotalKeySize> _deriveKey(const cpputils::DerivedKeyConfig &keyConfig, const std::string &password);
-        static boost::optional<std::string> _loadCipherName(const OuterEncryptor &outerEncryptor, const OuterConfig &outerConfig);
+        static cpputils::unique_ref<CryConfigEncryptor> _deriveKey(cpputils::unique_ref<cpputils::SCrypt> kdf, const std::string &password);
     };
 }
 
diff --git a/src/cryfs/config/crypto/inner/ConcreteInnerEncryptor.h b/src/cryfs/config/crypto/inner/ConcreteInnerEncryptor.h
index ea6d03fa..3f1c6e19 100644
--- a/src/cryfs/config/crypto/inner/ConcreteInnerEncryptor.h
+++ b/src/cryfs/config/crypto/inner/ConcreteInnerEncryptor.h
@@ -3,7 +3,6 @@
 #define MESSMER_CRYFS_SRC_CONFIG_CRYPTO_INNER_CONCRETECRYCONFIGENCRYPTOR_H
 
 #include <cpp-utils/crypto/RandomPadding.h>
-#include <cpp-utils/crypto/kdf/DerivedKey.h>
 
 #include "InnerEncryptor.h"
 #include "InnerConfig.h"
diff --git a/src/cryfs/config/crypto/outer/OuterConfig.cpp b/src/cryfs/config/crypto/outer/OuterConfig.cpp
index a206399c..7690687d 100644
--- a/src/cryfs/config/crypto/outer/OuterConfig.cpp
+++ b/src/cryfs/config/crypto/outer/OuterConfig.cpp
@@ -1,17 +1,21 @@
 #include "OuterConfig.h"
+#include <cpp-utils/crypto/kdf/SCryptParameters.h>
 
 using std::string;
 using std::exception;
 using cpputils::Data;
 using cpputils::Serializer;
 using cpputils::Deserializer;
-using cpputils::DerivedKeyConfig;
+using cpputils::SCryptParameters;
 using boost::optional;
 using boost::none;
 using namespace cpputils::logging;
 
 namespace cryfs {
-    const string OuterConfig::HEADER = "cryfs.config;0;scrypt";
+#ifndef CRYFS_NO_COMPATIBILITY
+    const string OuterConfig::OLD_HEADER = "cryfs.config;0;scrypt";
+#endif
+    const string OuterConfig::HEADER = "cryfs.config;1;scrypt";
 
     void OuterConfig::_checkHeader(Deserializer *deserializer) {
         string header = deserializer->readString();
@@ -27,10 +31,10 @@ namespace cryfs {
     Data OuterConfig::serialize() const {
         try {
             Serializer serializer(Serializer::StringSize(HEADER)
-                                  + keyConfig.serializedSize()
+                                  + Serializer::DataSize(kdfParameters)
                                   + encryptedInnerConfig.size());
             _writeHeader(&serializer);
-            keyConfig.serialize(&serializer);
+            serializer.writeData(kdfParameters);
             serializer.writeTailData(encryptedInnerConfig);
             return serializer.finished();
         } catch (const exception &e) {
@@ -42,14 +46,37 @@ namespace cryfs {
     optional<OuterConfig> OuterConfig::deserialize(const Data &data) {
         Deserializer deserializer(&data);
         try {
+#ifndef CRYFS_NO_COMPATIBILITY
+            string header = deserializer.readString();
+            if (header == OLD_HEADER) {
+                return _deserializeOldFormat(&deserializer);
+            } else if (header == HEADER) {
+                return _deserializeNewFormat(&deserializer);
+            } else {
+                throw std::runtime_error("Invalid header");
+            }
+#else
             _checkHeader(&deserializer);
-            auto keyConfig = DerivedKeyConfig::deserialize(&deserializer);
-            auto encryptedInnerConfig = deserializer.readTailData();
-            deserializer.finished();
-            return OuterConfig {std::move(keyConfig), std::move(encryptedInnerConfig)};
+            _deserializeNewFormat(&deserializer);
+#endif
         } catch (const exception &e) {
             LOG(ERROR) << "Error deserializing outer configuration: " << e.what();
             return none; // This can be caused by invalid input data and does not have to be a programming error. Don't throw exception.
         }
     }
+
+    OuterConfig OuterConfig::_deserializeOldFormat(Deserializer *deserializer) {
+        auto kdfParameters = SCryptParameters::deserializeOldFormat(deserializer);
+        auto kdfParametersSerialized = kdfParameters.serialize();
+        auto encryptedInnerConfig = deserializer->readTailData();
+        deserializer->finished();
+        return OuterConfig {std::move(kdfParametersSerialized), std::move(encryptedInnerConfig), true};
+    }
+
+    OuterConfig OuterConfig::_deserializeNewFormat(Deserializer *deserializer) {
+        auto kdfParameters = deserializer->readData();
+        auto encryptedInnerConfig = deserializer->readTailData();
+        deserializer->finished();
+        return OuterConfig {std::move(kdfParameters), std::move(encryptedInnerConfig), false};
+    }
 }
diff --git a/src/cryfs/config/crypto/outer/OuterConfig.h b/src/cryfs/config/crypto/outer/OuterConfig.h
index 2d1b85e0..c791654d 100644
--- a/src/cryfs/config/crypto/outer/OuterConfig.h
+++ b/src/cryfs/config/crypto/outer/OuterConfig.h
@@ -2,15 +2,15 @@
 #ifndef MESSMER_CRYFS_SRC_CONFIG_CRYPTO_OUTER_OUTERCONFIG_H
 #define MESSMER_CRYFS_SRC_CONFIG_CRYPTO_OUTER_OUTERCONFIG_H
 
-#include <cpp-utils/crypto/kdf/DerivedKeyConfig.h>
 #include <cpp-utils/data/Data.h>
 #include <cpp-utils/data/Serializer.h>
 #include <cpp-utils/data/Deserializer.h>
 
 namespace cryfs {
     struct OuterConfig final {
-        cpputils::DerivedKeyConfig keyConfig;
+        cpputils::Data kdfParameters;
         cpputils::Data encryptedInnerConfig;
+        bool wasInDeprecatedConfigFormat;
 
         cpputils::Data serialize() const;
         static boost::optional<OuterConfig> deserialize(const cpputils::Data &data);
@@ -18,8 +18,13 @@ namespace cryfs {
     private:
         static void _checkHeader(cpputils::Deserializer *deserializer);
         static void _writeHeader(cpputils::Serializer *serializer);
+        static OuterConfig _deserializeNewFormat(cpputils::Deserializer *deserializer);
 
         static const std::string HEADER;
+#ifndef CRYFS_NO_COMPATIBILITY
+        static const std::string OLD_HEADER;
+        static OuterConfig _deserializeOldFormat(cpputils::Deserializer *deserializer);
+#endif
     };
 }
 
diff --git a/src/cryfs/config/crypto/outer/OuterEncryptor.cpp b/src/cryfs/config/crypto/outer/OuterEncryptor.cpp
index e37e8220..4bfb2508 100644
--- a/src/cryfs/config/crypto/outer/OuterEncryptor.cpp
+++ b/src/cryfs/config/crypto/outer/OuterEncryptor.cpp
@@ -6,24 +6,23 @@ using std::string;
 using cpputils::unique_ref;
 using cpputils::Data;
 using cpputils::RandomPadding;
-using cpputils::DerivedKeyConfig;
 using boost::optional;
 using boost::none;
 using namespace cpputils::logging;
 
 namespace cryfs {
-    OuterEncryptor::OuterEncryptor(Cipher::EncryptionKey key, const cpputils::DerivedKeyConfig &keyConfig)
-            : _key(std::move(key)), _keyConfig(std::move(keyConfig)) {
+    OuterEncryptor::OuterEncryptor(Cipher::EncryptionKey key, cpputils::Data kdfParameters)
+            : _key(std::move(key)), _kdfParameters(std::move(kdfParameters)) {
     }
 
     OuterConfig OuterEncryptor::encrypt(const Data &plaintext) const {
         auto padded = RandomPadding::add(plaintext, CONFIG_SIZE);
         auto ciphertext = Cipher::encrypt(static_cast<const uint8_t*>(padded.data()), padded.size(), _key);
-        return OuterConfig{_keyConfig, std::move(ciphertext)};
+        return OuterConfig{_kdfParameters.copy(), std::move(ciphertext), false};
     }
 
     optional<Data> OuterEncryptor::decrypt(const OuterConfig &outerConfig) const {
-        ASSERT(outerConfig.keyConfig == _keyConfig, "OuterEncryptor was initialized with wrong key config");
+        ASSERT(outerConfig.kdfParameters == _kdfParameters, "OuterEncryptor was initialized with wrong key config");
         auto inner = Cipher::decrypt(static_cast<const uint8_t*>(outerConfig.encryptedInnerConfig.data()), outerConfig.encryptedInnerConfig.size(), _key);
         if(inner == none) {
             return none;
diff --git a/src/cryfs/config/crypto/outer/OuterEncryptor.h b/src/cryfs/config/crypto/outer/OuterEncryptor.h
index a7477488..ece3f7e2 100644
--- a/src/cryfs/config/crypto/outer/OuterEncryptor.h
+++ b/src/cryfs/config/crypto/outer/OuterEncryptor.h
@@ -14,7 +14,7 @@ namespace cryfs {
         using Cipher = cpputils::AES256_GCM;
         static constexpr size_t CONFIG_SIZE = 1024;  // Config data is grown to this size before encryption to hide its actual size
 
-        OuterEncryptor(Cipher::EncryptionKey key, const cpputils::DerivedKeyConfig &keyConfig);
+        OuterEncryptor(Cipher::EncryptionKey key, cpputils::Data kdfParameters);
 
         OuterConfig encrypt(const cpputils::Data &encryptedInnerConfig) const;
         boost::optional<cpputils::Data> decrypt(const OuterConfig &outerConfig) const;
@@ -22,7 +22,7 @@ namespace cryfs {
     private:
 
         Cipher::EncryptionKey _key;
-        cpputils::DerivedKeyConfig _keyConfig;
+        cpputils::Data _kdfParameters;
 
         DISALLOW_COPY_AND_ASSIGN(OuterEncryptor);
     };
diff --git a/test/cpp-utils/CMakeLists.txt b/test/cpp-utils/CMakeLists.txt
index dc132db6..5a2bc9f8 100644
--- a/test/cpp-utils/CMakeLists.txt
+++ b/test/cpp-utils/CMakeLists.txt
@@ -5,8 +5,7 @@ set(SOURCES
     crypto/symmetric/CipherTest.cpp
     crypto/symmetric/testutils/FakeAuthenticatedCipher.cpp
     crypto/kdf/SCryptTest.cpp
-    crypto/kdf/DerivedKeyTest.cpp
-    crypto/kdf/DerivedKeyConfigTest.cpp
+    crypto/kdf/SCryptParametersTest.cpp
     MacrosIncludeTest.cpp
     pointer/unique_ref_test.cpp
     pointer/cast_include_test.cpp
diff --git a/test/cpp-utils/crypto/kdf/DerivedKeyConfigTest.cpp b/test/cpp-utils/crypto/kdf/DerivedKeyConfigTest.cpp
deleted file mode 100644
index a8927500..00000000
--- a/test/cpp-utils/crypto/kdf/DerivedKeyConfigTest.cpp
+++ /dev/null
@@ -1,86 +0,0 @@
-#include <gtest/gtest.h>
-#include "cpp-utils/crypto/kdf/DerivedKeyConfig.h"
-#include "cpp-utils/data/DataFixture.h"
-#include <sstream>
-
-using namespace cpputils;
-
-class DerivedKeyConfigTest : public ::testing::Test {
-public:
-    DerivedKeyConfig SaveAndLoad(const DerivedKeyConfig &source) {
-        Serializer serializer(source.serializedSize());
-        source.serialize(&serializer);
-        Data serialized = serializer.finished();
-        Deserializer deserializer(&serialized);
-        return DerivedKeyConfig::deserialize(&deserializer);
-    }
-};
-
-TEST_F(DerivedKeyConfigTest, Salt) {
-    DerivedKeyConfig cfg(DataFixture::generate(32), 0, 0, 0);
-    EXPECT_EQ(DataFixture::generate(32), cfg.salt());
-}
-
-TEST_F(DerivedKeyConfigTest, Salt_Move) {
-    DerivedKeyConfig cfg(DataFixture::generate(32), 0, 0, 0);
-    DerivedKeyConfig moved = std::move(cfg);
-    EXPECT_EQ(DataFixture::generate(32), moved.salt());
-}
-
-TEST_F(DerivedKeyConfigTest, Salt_SaveAndLoad) {
-    DerivedKeyConfig cfg(DataFixture::generate(32), 0, 0, 0);
-    DerivedKeyConfig loaded = SaveAndLoad(cfg);
-    EXPECT_EQ(DataFixture::generate(32), loaded.salt());
-}
-
-TEST_F(DerivedKeyConfigTest, N) {
-    DerivedKeyConfig cfg(Data(0), 1024, 0, 0);
-    EXPECT_EQ(1024u, cfg.N());
-}
-
-TEST_F(DerivedKeyConfigTest, N_Move) {
-    DerivedKeyConfig cfg(Data(0), 1024, 0, 0);
-    DerivedKeyConfig moved = std::move(cfg);
-    EXPECT_EQ(1024u, moved.N());
-}
-
-TEST_F(DerivedKeyConfigTest, N_SaveAndLoad) {
-    DerivedKeyConfig cfg(Data(0), 1024, 0, 0);
-    DerivedKeyConfig loaded = SaveAndLoad(cfg);
-    EXPECT_EQ(1024u, loaded.N());
-}
-
-TEST_F(DerivedKeyConfigTest, r) {
-    DerivedKeyConfig cfg(Data(0), 0, 8, 0);
-    EXPECT_EQ(8u, cfg.r());
-}
-
-TEST_F(DerivedKeyConfigTest, r_Move) {
-    DerivedKeyConfig cfg(Data(0), 0, 8, 0);
-    DerivedKeyConfig moved = std::move(cfg);
-    EXPECT_EQ(8u, moved.r());
-}
-
-TEST_F(DerivedKeyConfigTest, r_SaveAndLoad) {
-    DerivedKeyConfig cfg(Data(0), 0, 8, 0);
-    DerivedKeyConfig loaded = SaveAndLoad(cfg);
-    EXPECT_EQ(8u, loaded.r());
-}
-
-TEST_F(DerivedKeyConfigTest, p) {
-    DerivedKeyConfig cfg(Data(0), 0, 0, 16);
-    EXPECT_EQ(16u, cfg.p());
-}
-
-TEST_F(DerivedKeyConfigTest, p_Move) {
-    DerivedKeyConfig cfg(Data(0), 0, 0, 16);
-    DerivedKeyConfig moved = std::move(cfg);
-    EXPECT_EQ(16u, moved.p());
-}
-
-
-TEST_F(DerivedKeyConfigTest, p_SaveAndLoad) {
-    DerivedKeyConfig cfg(Data(0), 0, 0, 16);
-    DerivedKeyConfig loaded = SaveAndLoad(cfg);
-    EXPECT_EQ(16u, loaded.p());
-}
\ No newline at end of file
diff --git a/test/cpp-utils/crypto/kdf/DerivedKeyTest.cpp b/test/cpp-utils/crypto/kdf/DerivedKeyTest.cpp
deleted file mode 100644
index c04ee187..00000000
--- a/test/cpp-utils/crypto/kdf/DerivedKeyTest.cpp
+++ /dev/null
@@ -1,18 +0,0 @@
-#include <gtest/gtest.h>
-#include "cpp-utils/crypto/kdf/DerivedKey.h"
-#include "cpp-utils/data/DataFixture.h"
-
-using namespace cpputils;
-
-TEST(DerivedKeyTest, Config) {
-    DerivedKey<32> key(DerivedKeyConfig(DataFixture::generate(32, 1), 1024, 8, 16), DataFixture::generateFixedSize<32>(2));
-    EXPECT_EQ(DataFixture::generate(32, 1), key.config().salt());
-    EXPECT_EQ(1024u, key.config().N());
-    EXPECT_EQ(8u, key.config().r());
-    EXPECT_EQ(16u, key.config().p());
-}
-
-TEST(DerivedKeyTest, Key) {
-    DerivedKey<32> key(DerivedKeyConfig(DataFixture::generate(32, 1), 1024, 8, 16), DataFixture::generateFixedSize<32>(2));
-    EXPECT_EQ(DataFixture::generateFixedSize<32>(2), key.key());
-}
diff --git a/test/cpp-utils/crypto/kdf/SCryptParametersTest.cpp b/test/cpp-utils/crypto/kdf/SCryptParametersTest.cpp
new file mode 100644
index 00000000..8f18fc42
--- /dev/null
+++ b/test/cpp-utils/crypto/kdf/SCryptParametersTest.cpp
@@ -0,0 +1,83 @@
+#include <gtest/gtest.h>
+#include <cpp-utils/crypto/kdf/SCryptParameters.h>
+#include <cpp-utils/data/DataFixture.h>
+#include <sstream>
+
+using namespace cpputils;
+
+class SCryptParametersTest : public ::testing::Test {
+public:
+    SCryptParameters SaveAndLoad(const SCryptParameters &source) {
+        Data serialized = source.serialize();
+        return SCryptParameters::deserialize(serialized);
+    }
+};
+
+TEST_F(SCryptParametersTest, Salt) {
+    SCryptParameters cfg(DataFixture::generate(32), 0, 0, 0);
+    EXPECT_EQ(DataFixture::generate(32), cfg.salt());
+}
+
+TEST_F(SCryptParametersTest, Salt_Move) {
+    SCryptParameters cfg(DataFixture::generate(32), 0, 0, 0);
+    SCryptParameters moved = std::move(cfg);
+    EXPECT_EQ(DataFixture::generate(32), moved.salt());
+}
+
+TEST_F(SCryptParametersTest, Salt_SaveAndLoad) {
+    SCryptParameters cfg(DataFixture::generate(32), 0, 0, 0);
+    SCryptParameters loaded = SaveAndLoad(cfg);
+    EXPECT_EQ(DataFixture::generate(32), loaded.salt());
+}
+
+TEST_F(SCryptParametersTest, N) {
+    SCryptParameters cfg(Data(0), 1024, 0, 0);
+    EXPECT_EQ(1024u, cfg.N());
+}
+
+TEST_F(SCryptParametersTest, N_Move) {
+    SCryptParameters cfg(Data(0), 1024, 0, 0);
+    SCryptParameters moved = std::move(cfg);
+    EXPECT_EQ(1024u, moved.N());
+}
+
+TEST_F(SCryptParametersTest, N_SaveAndLoad) {
+    SCryptParameters cfg(Data(0), 1024, 0, 0);
+    SCryptParameters loaded = SaveAndLoad(cfg);
+    EXPECT_EQ(1024u, loaded.N());
+}
+
+TEST_F(SCryptParametersTest, r) {
+    SCryptParameters cfg(Data(0), 0, 8, 0);
+    EXPECT_EQ(8u, cfg.r());
+}
+
+TEST_F(SCryptParametersTest, r_Move) {
+    SCryptParameters cfg(Data(0), 0, 8, 0);
+    SCryptParameters moved = std::move(cfg);
+    EXPECT_EQ(8u, moved.r());
+}
+
+TEST_F(SCryptParametersTest, r_SaveAndLoad) {
+    SCryptParameters cfg(Data(0), 0, 8, 0);
+    SCryptParameters loaded = SaveAndLoad(cfg);
+    EXPECT_EQ(8u, loaded.r());
+}
+
+TEST_F(SCryptParametersTest, p) {
+    SCryptParameters cfg(Data(0), 0, 0, 16);
+    EXPECT_EQ(16u, cfg.p());
+}
+
+TEST_F(SCryptParametersTest, p_Move) {
+    SCryptParameters cfg(Data(0), 0, 0, 16);
+    SCryptParameters moved = std::move(cfg);
+    EXPECT_EQ(16u, moved.p());
+}
+
+
+TEST_F(SCryptParametersTest, p_SaveAndLoad) {
+    SCryptParameters cfg(Data(0), 0, 0, 16);
+    SCryptParameters loaded = SaveAndLoad(cfg);
+    EXPECT_EQ(16u, loaded.p());
+}
\ No newline at end of file
diff --git a/test/cpp-utils/crypto/kdf/SCryptTest.cpp b/test/cpp-utils/crypto/kdf/SCryptTest.cpp
index ae12678e..275c1967 100644
--- a/test/cpp-utils/crypto/kdf/SCryptTest.cpp
+++ b/test/cpp-utils/crypto/kdf/SCryptTest.cpp
@@ -2,49 +2,65 @@
 #include "cpp-utils/crypto/kdf/Scrypt.h"
 
 using namespace cpputils;
+using std::string;
 
-TEST(SCryptTest, GeneratedKeyIsReproductible_448) {
-    auto created = SCrypt().generateKey<56>("mypassword", SCrypt::TestSettings);
-    auto recreated = SCrypt().generateKeyFromConfig<56>("mypassword", created.config());
-    EXPECT_EQ(created.key(), recreated);
+class SCryptTest : public ::testing::Test {
+public:
+    unique_ref<SCrypt> scryptForNewKey = SCrypt::forNewKey(SCrypt::TestSettings);
+    unique_ref<SCrypt> scryptForExistingKey = SCrypt::forExistingKey(scryptForNewKey->kdfParameters());
+
+    SCryptParameters kdfParameters(const SCrypt &scrypt) {
+        SCryptParameters result = SCryptParameters::deserialize(scrypt.kdfParameters());
+        return result;
+    }
+};
+
+TEST_F(SCryptTest, GeneratedKeyIsReproductible_448) {
+    auto derivedKey = scryptForNewKey->deriveKey<56>("mypassword");
+    auto rederivedKey = scryptForExistingKey->deriveKey<56>("mypassword");
+    EXPECT_EQ(derivedKey, rederivedKey);
 }
 
-TEST(SCryptTest, GeneratedKeyIsReproductible_256) {
-    auto created = SCrypt().generateKey<32>("mypassword", SCrypt::TestSettings);
-    auto recreated = SCrypt().generateKeyFromConfig<32>("mypassword", created.config());
-    EXPECT_EQ(created.key(), recreated);
+TEST_F(SCryptTest, GeneratedKeyIsReproductible_256) {
+    auto derivedKey = scryptForNewKey->deriveKey<32>("mypassword");
+    auto rederivedKey = scryptForExistingKey->deriveKey<32>("mypassword");
+    EXPECT_EQ(derivedKey, rederivedKey);
 }
 
-TEST(SCryptTest, GeneratedKeyIsReproductible_128) {
-    auto created = SCrypt().generateKey<16>("mypassword", SCrypt::TestSettings);
-    auto recreated = SCrypt().generateKeyFromConfig<16>("mypassword", created.config());
-    EXPECT_EQ(created.key(), recreated);
+TEST_F(SCryptTest, GeneratedKeyIsReproductible_128) {
+    auto derivedKey = scryptForNewKey->deriveKey<16>("mypassword");
+    auto rederivedKey = scryptForExistingKey->deriveKey<16>("mypassword");
+    EXPECT_EQ(derivedKey, rederivedKey);
 }
 
-TEST(SCryptTest, GeneratedKeyIsReproductible_DefaultSettings) {
-    auto created = SCrypt().generateKey<16>("mypassword", SCrypt::DefaultSettings);
-    auto recreated = SCrypt().generateKeyFromConfig<16>("mypassword", created.config());
-    EXPECT_EQ(created.key(), recreated);
+TEST_F(SCryptTest, GeneratedKeyIsReproductible_DefaultSettings) {
+    auto derivedKey = scryptForNewKey->deriveKey<16>("mypassword");
+    auto rederivedKey = scryptForExistingKey->deriveKey<16>("mypassword");
+    EXPECT_EQ(derivedKey, rederivedKey);
 }
 
-TEST(SCryptTest, DifferentPasswordResultsInDifferentKey) {
-    auto created = SCrypt().generateKey<16>("mypassword", SCrypt::TestSettings);
-    auto recreated = SCrypt().generateKeyFromConfig<16>("mypassword2", created.config());
-    EXPECT_NE(created.key(), recreated);
+TEST_F(SCryptTest, DifferentPasswordResultsInDifferentKey) {
+    auto derivedKey = scryptForNewKey->deriveKey<16>("mypassword");
+    auto rederivedKey = scryptForExistingKey->deriveKey<16>("mypassword2");
+    EXPECT_NE(derivedKey, rederivedKey);
 }
 
-TEST(SCryptTest, UsesCorrectSettings) {
-    auto created = SCrypt().generateKey<16>("mypassword", SCrypt::TestSettings);
-    EXPECT_EQ(SCrypt::TestSettings.SALT_LEN, created.config().salt().size());
-    EXPECT_EQ(SCrypt::TestSettings.N, created.config().N());
-    EXPECT_EQ(SCrypt::TestSettings.r, created.config().r());
-    EXPECT_EQ(SCrypt::TestSettings.p, created.config().p());
+TEST_F(SCryptTest, UsesCorrectSettings) {
+    auto scrypt = SCrypt::forNewKey(SCrypt::TestSettings);
+    auto derivedKey = scrypt->deriveKey<16>("mypassword");
+    SCryptParameters parameters = kdfParameters(*scrypt);
+    EXPECT_EQ(SCrypt::TestSettings.SALT_LEN, parameters.salt().size());
+    EXPECT_EQ(SCrypt::TestSettings.N, parameters.N());
+    EXPECT_EQ(SCrypt::TestSettings.r, parameters.r());
+    EXPECT_EQ(SCrypt::TestSettings.p, parameters.p());
 }
 
-TEST(SCryptTest, UsesCorrectDefaultSettings) {
-    auto created = SCrypt().generateKey<16>("mypassword", SCrypt::DefaultSettings);
-    EXPECT_EQ(SCrypt::DefaultSettings.SALT_LEN, created.config().salt().size());
-    EXPECT_EQ(SCrypt::DefaultSettings.N, created.config().N());
-    EXPECT_EQ(SCrypt::DefaultSettings.r, created.config().r());
-    EXPECT_EQ(SCrypt::DefaultSettings.p, created.config().p());
+TEST_F(SCryptTest, UsesCorrectDefaultSettings) {
+    auto scrypt = SCrypt::forNewKey(SCrypt::DefaultSettings);
+    auto derivedKey = scrypt->deriveKey<16>("mypassword");
+    SCryptParameters parameters = kdfParameters(*scrypt);
+    EXPECT_EQ(SCrypt::DefaultSettings.SALT_LEN, parameters.salt().size());
+    EXPECT_EQ(SCrypt::DefaultSettings.N, parameters.N());
+    EXPECT_EQ(SCrypt::DefaultSettings.r, parameters.r());
+    EXPECT_EQ(SCrypt::DefaultSettings.p, parameters.p());
 }
diff --git a/test/cryfs/config/crypto/CryConfigEncryptorTest.cpp b/test/cryfs/config/crypto/CryConfigEncryptorTest.cpp
index 1d4f46df..df046928 100644
--- a/test/cryfs/config/crypto/CryConfigEncryptorTest.cpp
+++ b/test/cryfs/config/crypto/CryConfigEncryptorTest.cpp
@@ -8,8 +8,7 @@ using cpputils::unique_ref;
 using cpputils::make_unique_ref;
 using cpputils::DataFixture;
 using cpputils::Data;
-using cpputils::DerivedKeyConfig;
-using cpputils::DerivedKey;
+using cpputils::FixedSizeData;
 using cpputils::AES128_CFB;
 using cpputils::AES256_GCM;
 using cpputils::Twofish256_GCM;
@@ -29,7 +28,7 @@ class CryConfigEncryptorTest: public ::testing::Test {
 public:
 
     unique_ref<CryConfigEncryptor> makeEncryptor() {
-        return make_unique_ref<CryConfigEncryptor>(_derivedKey());
+        return make_unique_ref<CryConfigEncryptor>(_derivedKey(), _kdfParameters());
     }
 
     Data changeInnerCipherFieldTo(Data data, const string &newCipherName) {
@@ -39,16 +38,17 @@ public:
     }
 
 private:
-    DerivedKey<CryConfigEncryptor::MaxTotalKeySize> _derivedKey() {
-        auto salt = DataFixture::generate(128, 2);
-        auto keyConfig = DerivedKeyConfig(std::move(salt), 1024, 1, 2);
-        auto key = DataFixture::generateFixedSize<CryConfigEncryptor::MaxTotalKeySize>(3);
-        return DerivedKey<CryConfigEncryptor::MaxTotalKeySize>(std::move(keyConfig), std::move(key));
+    FixedSizeData<CryConfigEncryptor::MaxTotalKeySize> _derivedKey() {
+        return DataFixture::generateFixedSize<CryConfigEncryptor::MaxTotalKeySize>(3);
+    }
+
+    Data _kdfParameters() {
+        return DataFixture::generate(128, 2);
     }
 
     unique_ref<OuterEncryptor> _outerEncryptor() {
-        auto outerKey = _derivedKey().key().take<CryConfigEncryptor::OuterKeySize>();
-        return make_unique_ref<OuterEncryptor>(outerKey, _derivedKey().config());
+        auto outerKey = _derivedKey().take<CryConfigEncryptor::OuterKeySize>();
+        return make_unique_ref<OuterEncryptor>(outerKey, _kdfParameters());
     }
 
     InnerConfig _decryptInnerConfig(const Data &data) {
diff --git a/test/cryfs/config/crypto/outer/OuterConfigTest.cpp b/test/cryfs/config/crypto/outer/OuterConfigTest.cpp
index 5a4627b4..ce96f3ed 100644
--- a/test/cryfs/config/crypto/outer/OuterConfigTest.cpp
+++ b/test/cryfs/config/crypto/outer/OuterConfigTest.cpp
@@ -4,7 +4,8 @@
 
 using cpputils::Data;
 using cpputils::DataFixture;
-using cpputils::DerivedKeyConfig;
+using cpputils::Deserializer;
+using cpputils::Serializer;
 using boost::none;
 using std::ostream;
 using namespace cryfs;
@@ -19,39 +20,36 @@ namespace boost {
 
 class OuterConfigTest: public ::testing::Test {
 public:
-    Data salt() {
+    Data kdfParameters() {
         return DataFixture::generate(128, 2);
     }
-    uint64_t N = 1024;
-    uint8_t r = 1;
-    uint8_t p = 2;
 };
 
 TEST_F(OuterConfigTest, SomeValues) {
-    Data serialized = OuterConfig{DerivedKeyConfig(salt(), N, r, p), DataFixture::generate(1024)}.serialize();
+    Data serialized = OuterConfig{kdfParameters(), DataFixture::generate(1024), false}.serialize();
     OuterConfig deserialized = OuterConfig::deserialize(serialized).value();
-    EXPECT_EQ(DerivedKeyConfig(salt(), N, r, p), deserialized.keyConfig);
+    EXPECT_EQ(kdfParameters(), deserialized.kdfParameters);
     EXPECT_EQ(DataFixture::generate(1024), deserialized.encryptedInnerConfig);
 }
 
 TEST_F(OuterConfigTest, DataEmpty) {
-    Data serialized = OuterConfig{DerivedKeyConfig(salt(), N, r, p), Data(0)}.serialize();
+    Data serialized = OuterConfig{kdfParameters(), Data(0), false}.serialize();
     OuterConfig deserialized = OuterConfig::deserialize(serialized).value();
-    EXPECT_EQ(DerivedKeyConfig(salt(), N, r, p), deserialized.keyConfig);
+    EXPECT_EQ(kdfParameters(), deserialized.kdfParameters);
     EXPECT_EQ(Data(0), deserialized.encryptedInnerConfig);
 }
 
 TEST_F(OuterConfigTest, KeyConfigEmpty) {
-    Data serialized = OuterConfig{DerivedKeyConfig(Data(0), 0, 0, 0), DataFixture::generate(1024)}.serialize();
+    Data serialized = OuterConfig{Data(0), DataFixture::generate(1024), false}.serialize();
     OuterConfig deserialized = OuterConfig::deserialize(serialized).value();
-    EXPECT_EQ(DerivedKeyConfig(Data(0), 0, 0, 0), deserialized.keyConfig);
+    EXPECT_EQ(Data(0), deserialized.kdfParameters);
     EXPECT_EQ(DataFixture::generate(1024), deserialized.encryptedInnerConfig);
 }
 
 TEST_F(OuterConfigTest, DataAndKeyConfigEmpty) {
-    Data serialized = OuterConfig{DerivedKeyConfig(Data(0), 0, 0, 0), Data(0)}.serialize();
+    Data serialized = OuterConfig{Data(0), Data(0), false}.serialize();
     OuterConfig deserialized = OuterConfig::deserialize(serialized).value();
-    EXPECT_EQ(DerivedKeyConfig(Data(0), 0, 0, 0), deserialized.keyConfig);
+    EXPECT_EQ(Data(0), deserialized.kdfParameters);
     EXPECT_EQ(Data(0), deserialized.encryptedInnerConfig);
 }
 
diff --git a/test/cryfs/config/crypto/outer/OuterEncryptorTest.cpp b/test/cryfs/config/crypto/outer/OuterEncryptorTest.cpp
index 9f1a644d..7fa5fe65 100644
--- a/test/cryfs/config/crypto/outer/OuterEncryptorTest.cpp
+++ b/test/cryfs/config/crypto/outer/OuterEncryptorTest.cpp
@@ -9,7 +9,6 @@ using cpputils::Data;
 using cpputils::DataFixture;
 using cpputils::unique_ref;
 using cpputils::make_unique_ref;
-using cpputils::DerivedKeyConfig;
 using namespace cryfs;
 
 // This is needed for google test
@@ -22,10 +21,13 @@ namespace boost {
 
 class OuterEncryptorTest : public ::testing::Test {
 public:
+    Data kdfParameters() {
+        return DataFixture::generate(128);
+    }
+
     unique_ref<OuterEncryptor> makeOuterEncryptor() {
         auto key = DataFixture::generateFixedSize<OuterEncryptor::Cipher::EncryptionKey::BINARY_LENGTH>();
-        auto salt = DataFixture::generate(128);
-        return make_unique_ref<OuterEncryptor>(key, DerivedKeyConfig(std::move(salt), 1024, 1, 2));
+        return make_unique_ref<OuterEncryptor>(key, kdfParameters());
     }
 };