diff --git a/libsession-util/libsession-util b/libsession-util/libsession-util
index 3eb9eb7923..e2eed34ef2 160000
--- a/libsession-util/libsession-util
+++ b/libsession-util/libsession-util
@@ -1 +1 @@
-Subproject commit 3eb9eb79235d8454aa6fc56278230a1fa26c9fb7
+Subproject commit e2eed34ef25b3076a29000e43163bda832793159
diff --git a/libsession-util/src/main/cpp/CMakeLists.txt b/libsession-util/src/main/cpp/CMakeLists.txt
index 97fc9a1817..c41413161d 100644
--- a/libsession-util/src/main/cpp/CMakeLists.txt
+++ b/libsession-util/src/main/cpp/CMakeLists.txt
@@ -10,7 +10,7 @@ cmake_minimum_required(VERSION 3.18.1)
 project("session_util")
 
 # Compiles in C++17 mode
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
diff --git a/libsession-util/src/main/cpp/blinded_key.cpp b/libsession-util/src/main/cpp/blinded_key.cpp
index 1ed1cfd554..fd2109be20 100644
--- a/libsession-util/src/main/cpp/blinded_key.cpp
+++ b/libsession-util/src/main/cpp/blinded_key.cpp
@@ -14,11 +14,11 @@ Java_network_loki_messenger_libsession_1util_util_BlindKeyAPI_blindVersionKeyPai
                                                                                   jobject thiz,
                                                                                   jbyteArray ed25519_secret_key) {
     return jni_utils::run_catching_cxx_exception_or_throws<jobject>(env, [=] {
-        const auto [pk, sk] = session::blind_version_key_pair(util::ustring_from_bytes(env, ed25519_secret_key));
+        const auto [pk, sk] = session::blind_version_key_pair(util::vector_from_bytes(env, ed25519_secret_key));
 
         jclass kp_class = env->FindClass("network/loki/messenger/libsession_util/util/KeyPair");
         jmethodID kp_constructor = env->GetMethodID(kp_class, "<init>", "([B[B)V");
-        return env->NewObject(kp_class, kp_constructor, util::bytes_from_ustring(env, {pk.data(), pk.size()}), util::bytes_from_ustring(env, {sk.data(), sk.size()}));
+        return env->NewObject(kp_class, kp_constructor, util::bytes_from_vector(env, {pk.data(), pk.data() + pk.size()}), util::bytes_from_vector(env, {sk.data(), sk.data() + sk.size()}));
     });
 }
 extern "C"
@@ -28,7 +28,7 @@ Java_network_loki_messenger_libsession_1util_util_BlindKeyAPI_blindVersionSign(J
                                                                                jbyteArray ed25519_secret_key,
                                                                                jlong timestamp) {
     return jni_utils::run_catching_cxx_exception_or_throws<jbyteArray>(env, [=] {
-        auto bytes = session::blind_version_sign(util::ustring_from_bytes(env, ed25519_secret_key), session::Platform::android, timestamp);
-        return util::bytes_from_ustring(env, bytes);
+        auto bytes = session::blind_version_sign(util::vector_from_bytes(env, ed25519_secret_key), session::Platform::android, timestamp);
+        return util::bytes_from_vector(env, bytes);
     });
 }
\ No newline at end of file
diff --git a/libsession-util/src/main/cpp/config_base.cpp b/libsession-util/src/main/cpp/config_base.cpp
index 8017d2bc7d..795c988d49 100644
--- a/libsession-util/src/main/cpp/config_base.cpp
+++ b/libsession-util/src/main/cpp/config_base.cpp
@@ -32,7 +32,7 @@ Java_network_loki_messenger_libsession_1util_ConfigBase_push(JNIEnv *env, jobjec
     auto to_push_str = std::get<1>(push_tuple);
     auto to_delete = std::get<2>(push_tuple);
 
-    jbyteArray returnByteArray = util::bytes_from_ustring(env, to_push_str);
+    jbyteArray returnByteArray = util::bytes_from_vector(env, to_push_str);
     jlong seqNo = std::get<0>(push_tuple);
     jclass returnObjectClass = env->FindClass("network/loki/messenger/libsession_util/util/ConfigPush");
     jclass stackClass = env->FindClass("java/util/Stack");
@@ -59,7 +59,7 @@ Java_network_loki_messenger_libsession_1util_ConfigBase_dump(JNIEnv *env, jobjec
     std::lock_guard lock{util::util_mutex_};
     auto config = ptrToConfigBase(env, thiz);
     auto dumped = config->dump();
-    jbyteArray bytes = util::bytes_from_ustring(env, dumped);
+    jbyteArray bytes = util::bytes_from_vector(env, dumped);
     return bytes;
 }
 
@@ -90,7 +90,7 @@ Java_network_loki_messenger_libsession_1util_ConfigBase_merge___3Lkotlin_Pair_2(
         std::lock_guard lock{util::util_mutex_};
         auto conf = ptrToConfigBase(env, thiz);
         size_t number = env->GetArrayLength(to_merge);
-        std::vector<std::pair<std::string, session::ustring>> configs = {};
+        std::vector<std::pair<std::string, std::vector<unsigned char>>> configs = {};
         for (int i = 0; i < number; i++) {
             auto jElement = (jobject) env->GetObjectArrayElement(to_merge, i);
             auto pair = extractHashAndData(env, jElement);
diff --git a/libsession-util/src/main/cpp/config_base.h b/libsession-util/src/main/cpp/config_base.h
index 3f6e6ceba8..e80f13d68a 100644
--- a/libsession-util/src/main/cpp/config_base.h
+++ b/libsession-util/src/main/cpp/config_base.h
@@ -12,15 +12,15 @@ inline session::config::ConfigBase* ptrToConfigBase(JNIEnv *env, jobject obj) {
     return (session::config::ConfigBase*) env->GetLongField(obj, pointerField);
 }
 
-inline std::pair<std::string, session::ustring> extractHashAndData(JNIEnv *env, jobject kotlin_pair) {
+inline std::pair<std::string, std::vector<unsigned char>> extractHashAndData(JNIEnv *env, jobject kotlin_pair) {
     jclass pair = env->FindClass("kotlin/Pair");
     jfieldID first = env->GetFieldID(pair, "first", "Ljava/lang/Object;");
     jfieldID second = env->GetFieldID(pair, "second", "Ljava/lang/Object;");
     jstring hash_as_jstring = static_cast<jstring>(env->GetObjectField(kotlin_pair, first));
     jbyteArray data_as_jbytes = static_cast<jbyteArray>(env->GetObjectField(kotlin_pair, second));
     auto hash_as_string = env->GetStringUTFChars(hash_as_jstring, nullptr);
-    auto data_as_ustring = util::ustring_from_bytes(env, data_as_jbytes);
-    auto ret_pair = std::pair<std::string, session::ustring>{hash_as_string, data_as_ustring};
+    auto data_as_vector = util::vector_from_bytes(env, data_as_jbytes);
+    auto ret_pair = std::pair<std::string, std::vector<unsigned char>>{hash_as_string, data_as_vector};
     env->ReleaseStringUTFChars(hash_as_jstring, hash_as_string);
     return ret_pair;
 }
diff --git a/libsession-util/src/main/cpp/config_common.cpp b/libsession-util/src/main/cpp/config_common.cpp
index 848c816bf7..1da3fb4bfa 100644
--- a/libsession-util/src/main/cpp/config_common.cpp
+++ b/libsession-util/src/main/cpp/config_common.cpp
@@ -17,9 +17,9 @@ Java_network_loki_messenger_libsession_1util_ConfigKt_createConfigObject(
         jbyteArray initial_dump) {
     return jni_utils::run_catching_cxx_exception_or_throws<jlong>(env, [=] {
         auto config_name = util::string_from_jstring(env, java_config_name);
-        auto secret_key = util::ustring_from_bytes(env, ed25519_secret_key);
+        auto secret_key = util::vector_from_bytes(env, ed25519_secret_key);
         auto initial = initial_dump
-                       ? std::optional(util::ustring_from_bytes(env, initial_dump))
+                       ? std::optional(util::vector_from_bytes(env, initial_dump))
                        : std::nullopt;
 
 
diff --git a/libsession-util/src/main/cpp/contacts.h b/libsession-util/src/main/cpp/contacts.h
index f091e195ea..4108352e07 100644
--- a/libsession-util/src/main/cpp/contacts.h
+++ b/libsession-util/src/main/cpp/contacts.h
@@ -2,6 +2,7 @@
 #define SESSION_ANDROID_CONTACTS_H
 
 #include <jni.h>
+#include <vector>
 #include "session/config/contacts.hpp"
 #include "util.h"
 
@@ -58,7 +59,7 @@ inline session::config::contact_info deserialize_contact(JNIEnv *env, jobject in
     auto expiry_pair = util::deserialize_expiry(env, expiry_mode);
 
     std::string url;
-    session::ustring key;
+    std::vector<unsigned char> key;
 
     if (user_pic != nullptr) {
         auto deserialized_pic = util::deserialize_user_pic(env, user_pic);
@@ -66,7 +67,7 @@ inline session::config::contact_info deserialize_contact(JNIEnv *env, jobject in
         auto url_bytes = env->GetStringUTFChars(url_jstring, nullptr);
         url = std::string(url_bytes);
         env->ReleaseStringUTFChars(url_jstring, url_bytes);
-        key = util::ustring_from_bytes(env, deserialized_pic.second);
+        key = util::vector_from_bytes(env, deserialized_pic.second);
     }
 
     auto account_id_bytes = env->GetStringUTFChars(account_id, nullptr);
diff --git a/libsession-util/src/main/cpp/conversation.cpp b/libsession-util/src/main/cpp/conversation.cpp
index 3fb322533b..19f5f6f4e2 100644
--- a/libsession-util/src/main/cpp/conversation.cpp
+++ b/libsession-util/src/main/cpp/conversation.cpp
@@ -152,8 +152,8 @@ Java_network_loki_messenger_libsession_1util_ConversationVolatileConfig_getOrCon
     auto convos = ptrToConvoInfo(env, thiz);
     auto base_url_chars = env->GetStringUTFChars(base_url, nullptr);
     auto room_chars = env->GetStringUTFChars(room, nullptr);
-    auto pub_key_ustring = util::ustring_from_bytes(env, pub_key);
-    auto open = convos->get_or_construct_community(base_url_chars, room_chars, pub_key_ustring);
+    auto pub_key_vector = util::vector_from_bytes(env, pub_key);
+    auto open = convos->get_or_construct_community(base_url_chars, room_chars, pub_key_vector);
     auto serialized = serialize_open_group(env, open);
     return serialized;
 }
diff --git a/libsession-util/src/main/cpp/group_info.cpp b/libsession-util/src/main/cpp/group_info.cpp
index c80db46d2a..79f173d6e7 100644
--- a/libsession-util/src/main/cpp/group_info.cpp
+++ b/libsession-util/src/main/cpp/group_info.cpp
@@ -10,15 +10,15 @@ Java_network_loki_messenger_libsession_1util_GroupInfoConfig_00024Companion_newI
                                                                                         jbyteArray secret_key,
                                                                                         jbyteArray initial_dump) {
     std::lock_guard guard{util::util_mutex_};
-    std::optional<session::ustring> secret_key_optional{std::nullopt};
-    std::optional<session::ustring> initial_dump_optional{std::nullopt};
-    auto pub_key_bytes = util::ustring_from_bytes(env, pub_key);
+    std::optional<std::vector<unsigned char>> secret_key_optional{std::nullopt};
+    std::optional<std::vector<unsigned char>> initial_dump_optional{std::nullopt};
+    auto pub_key_bytes = util::vector_from_bytes(env, pub_key);
     if (secret_key && env->GetArrayLength(secret_key) > 0) {
-        auto secret_key_bytes = util::ustring_from_bytes(env, secret_key);
+        auto secret_key_bytes = util::vector_from_bytes(env, secret_key);
         secret_key_optional = secret_key_bytes;
     }
     if (initial_dump && env->GetArrayLength(initial_dump) > 0) {
-        auto initial_dump_bytes = util::ustring_from_bytes(env, initial_dump);
+        auto initial_dump_bytes = util::vector_from_bytes(env, initial_dump);
         initial_dump_optional = initial_dump_bytes;
     }
 
@@ -159,7 +159,7 @@ Java_network_loki_messenger_libsession_1util_GroupInfoConfig_setProfilePic(JNIEn
     auto group_info = ptrToInfo(env, thiz);
     auto user_pic = util::deserialize_user_pic(env, new_profile_pic);
     auto url = env->GetStringUTFChars(user_pic.first, nullptr);
-    auto key = util::ustring_from_bytes(env, user_pic.second);
+    auto key = util::vector_from_bytes(env, user_pic.second);
     group_info->set_profile_pic(url, key);
     env->ReleaseStringUTFChars(user_pic.first, url);
 }
diff --git a/libsession-util/src/main/cpp/group_keys.cpp b/libsession-util/src/main/cpp/group_keys.cpp
index d70d1aa36e..8a5a16707c 100644
--- a/libsession-util/src/main/cpp/group_keys.cpp
+++ b/libsession-util/src/main/cpp/group_keys.cpp
@@ -23,18 +23,18 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_00024Companion_newI
                                                                                         jlong members_pointer) {
     return jni_utils::run_catching_cxx_exception_or_throws<jlong>(env, [=] {
         std::lock_guard lock{util::util_mutex_};
-        auto user_key_bytes = util::ustring_from_bytes(env, user_secret_key);
-        auto pub_key_bytes = util::ustring_from_bytes(env, group_public_key);
-        std::optional<session::ustring> secret_key_optional{std::nullopt};
-        std::optional<session::ustring> initial_dump_optional{std::nullopt};
+        auto user_key_bytes = util::vector_from_bytes(env, user_secret_key);
+        auto pub_key_bytes = util::vector_from_bytes(env, group_public_key);
+        std::optional<std::vector<unsigned char>> secret_key_optional{std::nullopt};
+        std::optional<std::vector<unsigned char>> initial_dump_optional{std::nullopt};
 
         if (group_secret_key && env->GetArrayLength(group_secret_key) > 0) {
-            auto secret_key_bytes = util::ustring_from_bytes(env, group_secret_key);
+            auto secret_key_bytes = util::vector_from_bytes(env, group_secret_key);
             secret_key_optional = secret_key_bytes;
         }
 
         if (initial_dump && env->GetArrayLength(initial_dump) > 0) {
-            auto initial_dump_bytes = util::ustring_from_bytes(env, initial_dump);
+            auto initial_dump_bytes = util::vector_from_bytes(env, initial_dump);
             initial_dump_optional = initial_dump_bytes;
         }
 
@@ -63,7 +63,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_groupKeys(JNIEnv *e
     jobject our_stack = env->NewObject(stack, init);
     jmethodID push = env->GetMethodID(stack, "push", "(Ljava/lang/Object;)Ljava/lang/Object;");
     for (auto& key : keys) {
-        auto key_bytes = util::bytes_from_ustring(env, key.data());
+        auto key_bytes = util::bytes_from_span(env, key);
         env->CallObjectMethod(our_stack, push, key_bytes);
     }
     return our_stack;
@@ -79,7 +79,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_loadKey(JNIEnv *env
                                                                      jlong members_ptr) {
     std::lock_guard lock{util::util_mutex_};
     auto keys = ptrToKeys(env, thiz);
-    auto message_bytes = util::ustring_from_bytes(env, message);
+    auto message_bytes = util::vector_from_bytes(env, message);
     auto hash_bytes = env->GetStringUTFChars(hash, nullptr);
     auto info = reinterpret_cast<session::config::groups::Info*>(info_ptr);
     auto members = reinterpret_cast<session::config::groups::Members*>(members_ptr);
@@ -119,7 +119,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_pendingKey(JNIEnv *
     if (!pending) {
         return nullptr;
     }
-    auto pending_bytes = util::bytes_from_ustring(env, *pending);
+    auto pending_bytes = util::bytes_from_span(env, *pending);
     return pending_bytes;
 }
 
@@ -133,7 +133,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_pendingConfig(JNIEn
     if (!pending) {
         return nullptr;
     }
-    auto pending_bytes = util::bytes_from_ustring(env, *pending);
+    auto pending_bytes = util::bytes_from_span(env, *pending);
     return pending_bytes;
 }
 
@@ -146,7 +146,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_rekey(JNIEnv *env,
     auto info = reinterpret_cast<session::config::groups::Info*>(info_ptr);
     auto members = reinterpret_cast<session::config::groups::Members*>(members_ptr);
     auto rekey = keys->rekey(*info, *members);
-    auto rekey_bytes = util::bytes_from_ustring(env, rekey.data());
+    auto rekey_bytes = util::bytes_from_span(env, rekey);
     return rekey_bytes;
 }
 
@@ -156,7 +156,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_dump(JNIEnv *env, j
     std::lock_guard lock{util::util_mutex_};
     auto keys = ptrToKeys(env, thiz);
     auto dump = keys->dump();
-    auto byte_array = util::bytes_from_ustring(env, dump);
+    auto byte_array = util::bytes_from_vector(env, dump);
     return byte_array;
 }
 
@@ -175,9 +175,9 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_encrypt(JNIEnv *env
     return jni_utils::run_catching_cxx_exception_or_throws<jbyteArray>(env, [=] {
         std::lock_guard lock{util::util_mutex_};
         auto ptr = ptrToKeys(env, thiz);
-        auto plaintext_ustring = util::ustring_from_bytes(env, plaintext);
-        auto enc = ptr->encrypt_message(plaintext_ustring);
-        return util::bytes_from_ustring(env, enc);
+        auto plaintext_vector = util::vector_from_bytes(env, plaintext);
+        auto enc = ptr->encrypt_message(plaintext_vector);
+        return util::bytes_from_vector(env, enc);
     });
 }
 
@@ -188,11 +188,11 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_decrypt(JNIEnv *env
     return jni_utils::run_catching_cxx_exception_or_throws<jobject>(env, [=] {
         std::lock_guard lock{util::util_mutex_};
         auto ptr = ptrToKeys(env, thiz);
-        auto ciphertext_ustring = util::ustring_from_bytes(env, ciphertext);
-        auto decrypted = ptr->decrypt_message(ciphertext_ustring);
+        auto ciphertext_vector = util::vector_from_bytes(env, ciphertext);
+        auto decrypted = ptr->decrypt_message(ciphertext_vector);
         auto sender = decrypted.first;
         auto plaintext = decrypted.second;
-        auto plaintext_bytes = util::bytes_from_ustring(env, plaintext);
+        auto plaintext_bytes = util::bytes_from_vector(env, plaintext);
         auto sender_session_id = util::serialize_account_id(env, sender.data());
         auto pair_class = env->FindClass("kotlin/Pair");
         auto pair_constructor = env->GetMethodID(pair_class, "<init>", "(Ljava/lang/Object;Ljava/lang/Object;)V");
@@ -212,7 +212,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_keys(JNIEnv *env, j
     jobject our_stack = env->NewObject(stack, init);
     jmethodID push = env->GetMethodID(stack, "push", "(Ljava/lang/Object;)Ljava/lang/Object;");
     for (auto& key : keys) {
-        auto key_bytes = util::bytes_from_ustring(env, key);
+        auto key_bytes = util::bytes_from_span(env, key);
         env->CallObjectMethod(our_stack, push, key_bytes);
     }
     return our_stack;
@@ -246,7 +246,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_makeSubAccount(JNIE
     auto ptr = ptrToKeys(env, thiz);
     auto deserialized_id = util::deserialize_account_id(env, session_id);
     auto new_subaccount_key = ptr->swarm_make_subaccount(deserialized_id.data(), can_write, can_delete);
-    auto jbytes = util::bytes_from_ustring(env, new_subaccount_key);
+    auto jbytes = util::bytes_from_vector(env, new_subaccount_key);
     return jbytes;
 }
 
@@ -261,7 +261,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_getSubAccountToken(
     auto ptr = ptrToKeys(env, thiz);
     auto deserialized_id = util::deserialize_account_id(env, session_id);
     auto token = ptr->swarm_subaccount_token(deserialized_id, can_write, can_delete);
-    auto jbytes = util::bytes_from_ustring(env, token);
+    auto jbytes = util::bytes_from_vector(env, token);
     return jbytes;
 }
 
@@ -273,9 +273,9 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_subAccountSign(JNIE
                                                                             jbyteArray signing_value) {
     std::lock_guard lock{util::util_mutex_};
     auto ptr = ptrToKeys(env, thiz);
-    auto message_ustring = util::ustring_from_bytes(env, message);
-    auto signing_value_ustring = util::ustring_from_bytes(env, signing_value);
-    auto swarm_auth = ptr->swarm_subaccount_sign(message_ustring, signing_value_ustring, false);
+    auto message_vector = util::vector_from_bytes(env, message);
+    auto signing_value_vector = util::vector_from_bytes(env, signing_value);
+    auto swarm_auth = ptr->swarm_subaccount_sign(message_vector, signing_value_vector, false);
     return util::deserialize_swarm_auth(env, swarm_auth);
 }
 
@@ -291,7 +291,7 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_supplementFor(JNIEn
         user_session_ids.push_back(util::string_from_jstring(env, (jstring)(env->GetObjectArrayElement(j_user_session_ids, i))));
     }
     auto supplement = ptr->key_supplement(user_session_ids);
-    return util::bytes_from_ustring(env, supplement);
+    return util::bytes_from_vector(env, supplement);
 }
 extern "C"
 JNIEXPORT jint JNICALL
@@ -326,11 +326,11 @@ Java_network_loki_messenger_libsession_1util_GroupKeysConfig_loadAdminKey(JNIEnv
                                                                           jlong members_ptr) {
     std::lock_guard lock{util::util_mutex_};
     auto ptr = ptrToKeys(env, thiz);
-    auto admin_key_ustring = util::ustring_from_bytes(env, admin_key);
+    auto admin_key_vector = util::vector_from_bytes(env, admin_key);
     auto info = reinterpret_cast<session::config::groups::Info*>(info_ptr);
     auto members = reinterpret_cast<session::config::groups::Members*>(members_ptr);
 
     jni_utils::run_catching_cxx_exception_or_throws<void>(env, [&] {
-        ptr->load_admin_key(admin_key_ustring, *info, *members);
+        ptr->load_admin_key(admin_key_vector, *info, *members);
     });
 }
diff --git a/libsession-util/src/main/cpp/group_members.cpp b/libsession-util/src/main/cpp/group_members.cpp
index 7d4dd58cf2..952f3d735a 100644
--- a/libsession-util/src/main/cpp/group_members.cpp
+++ b/libsession-util/src/main/cpp/group_members.cpp
@@ -8,15 +8,15 @@ Java_network_loki_messenger_libsession_1util_GroupMembersConfig_00024Companion_n
         JNIEnv *env, jobject thiz, jbyteArray pub_key, jbyteArray secret_key,
         jbyteArray initial_dump) {
     std::lock_guard lock{util::util_mutex_};
-    auto pub_key_bytes = util::ustring_from_bytes(env, pub_key);
-    std::optional<session::ustring> secret_key_optional{std::nullopt};
-    std::optional<session::ustring> initial_dump_optional{std::nullopt};
+    auto pub_key_bytes = util::vector_from_bytes(env, pub_key);
+    std::optional<std::vector<unsigned char>> secret_key_optional{std::nullopt};
+    std::optional<std::vector<unsigned char>> initial_dump_optional{std::nullopt};
     if (secret_key && env->GetArrayLength(secret_key) > 0) {
-        auto secret_key_bytes = util::ustring_from_bytes(env, secret_key);
+        auto secret_key_bytes = util::vector_from_bytes(env, secret_key);
         secret_key_optional = secret_key_bytes;
     }
     if (initial_dump && env->GetArrayLength(initial_dump) > 0) {
-        auto initial_dump_bytes = util::ustring_from_bytes(env, initial_dump);
+        auto initial_dump_bytes = util::vector_from_bytes(env, initial_dump);
         initial_dump_optional = initial_dump_bytes;
     }
 
@@ -209,7 +209,7 @@ Java_network_loki_messenger_libsession_1util_util_GroupMember_setProfilePic(JNIE
                                                                             jobject pic) {
     const auto [jurl, jkey] = util::deserialize_user_pic(env, pic);
     auto url = util::string_from_jstring(env, jurl);
-    auto key = util::ustring_from_bytes(env, jkey);
+    auto key = util::vector_from_bytes(env, jkey);
     auto &picture = ptrToMember(env, thiz)->profile_picture;
     picture.url = url;
     picture.key = key;
diff --git a/libsession-util/src/main/cpp/user_groups.cpp b/libsession-util/src/main/cpp/user_groups.cpp
index b34d56e825..029f7a00ae 100644
--- a/libsession-util/src/main/cpp/user_groups.cpp
+++ b/libsession-util/src/main/cpp/user_groups.cpp
@@ -339,8 +339,8 @@ Java_network_loki_messenger_libsession_1util_util_GroupInfo_00024ClosedGroupInfo
 
     auto seed_bytes = env->GetByteArrayElements(seed, nullptr);
     auto admin_key = session::ed25519::ed25519_key_pair(
-            session::ustring_view(reinterpret_cast<unsigned char *>(seed_bytes), 32)).second;
+            std::span<const unsigned char>(reinterpret_cast<const unsigned char *>(seed_bytes), 32)).second;
     env->ReleaseByteArrayElements(seed, seed_bytes, 0);
 
-    return util::bytes_from_ustring(env, session::ustring_view(admin_key.data(), admin_key.size()));
+    return util::bytes_from_span(env, std::span<const unsigned char>(admin_key.data(), admin_key.size()));
 }
\ No newline at end of file
diff --git a/libsession-util/src/main/cpp/user_groups.h b/libsession-util/src/main/cpp/user_groups.h
index 265af68013..8282cd0db7 100644
--- a/libsession-util/src/main/cpp/user_groups.h
+++ b/libsession-util/src/main/cpp/user_groups.h
@@ -62,8 +62,8 @@ inline session::config::legacy_group_info deserialize_legacy_group_info(JNIEnv *
 
     auto id_bytes = util::string_from_jstring(env, id);
     auto name_bytes = env->GetStringUTFChars(name, nullptr);
-    auto enc_pub_key_bytes = util::ustring_from_bytes(env, enc_pub_key);
-    auto enc_sec_key_bytes = util::ustring_from_bytes(env, enc_sec_key);
+    auto enc_pub_key_bytes = util::vector_from_bytes(env, enc_pub_key);
+    auto enc_sec_key_bytes = util::vector_from_bytes(env, enc_sec_key);
 
     auto info_deserialized = conf->get_or_construct_legacy_group(id_bytes);
 
@@ -115,8 +115,8 @@ inline jobject serialize_legacy_group_info(JNIEnv *env, session::config::legacy_
     jstring account_id = env->NewStringUTF(info.session_id.data());
     jstring name = env->NewStringUTF(info.name.data());
     jobject members = serialize_members(env, info.members());
-    jbyteArray enc_pubkey = util::bytes_from_ustring(env, info.enc_pubkey);
-    jbyteArray enc_seckey = util::bytes_from_ustring(env, info.enc_seckey);
+    jbyteArray enc_pubkey = util::bytes_from_vector(env, info.enc_pubkey);
+    jbyteArray enc_seckey = util::bytes_from_vector(env, info.enc_seckey);
     long long priority = info.priority;
     long long joined_at = info.joined_at;
 
@@ -128,8 +128,8 @@ inline jobject serialize_legacy_group_info(JNIEnv *env, session::config::legacy_
 
 inline jobject serialize_closed_group_info(JNIEnv* env, session::config::group_info info) {
     auto session_id = util::serialize_account_id(env, info.id);
-    jbyteArray admin_bytes = info.secretkey.empty() ? nullptr : util::bytes_from_ustring(env, info.secretkey);
-    jbyteArray auth_bytes = info.auth_data.empty() ? nullptr : util::bytes_from_ustring(env, info.auth_data);
+    jbyteArray admin_bytes = info.secretkey.empty() ? nullptr : util::bytes_from_vector(env, info.secretkey);
+    jbyteArray auth_bytes = info.auth_data.empty() ? nullptr : util::bytes_from_vector(env, info.auth_data);
     jstring name = util::jstringFromOptional(env, info.name);
 
     jclass group_info_class = env->FindClass("network/loki/messenger/libsession_util/util/GroupInfo$ClosedGroupInfo");
@@ -159,8 +159,8 @@ inline session::config::group_info deserialize_closed_group_info(JNIEnv* env, jo
     jstring name_jstring = (jstring)env->GetObjectField(info_serialized, name_field);
 
     auto id_bytes = util::deserialize_account_id(env, id_jobject);
-    auto secret_bytes = util::ustring_from_bytes(env, secret_jBytes);
-    auto auth_bytes = util::ustring_from_bytes(env, auth_jBytes);
+    auto secret_bytes = util::vector_from_bytes(env, secret_jBytes);
+    auto auth_bytes = util::vector_from_bytes(env, auth_jBytes);
     auto name = util::string_from_jstring(env, name_jstring);
 
     session::config::group_info group_info(id_bytes);
diff --git a/libsession-util/src/main/cpp/user_profile.cpp b/libsession-util/src/main/cpp/user_profile.cpp
index 47def9b6b5..254a561c66 100644
--- a/libsession-util/src/main/cpp/user_profile.cpp
+++ b/libsession-util/src/main/cpp/user_profile.cpp
@@ -42,7 +42,7 @@ Java_network_loki_messenger_libsession_1util_UserProfile_setPic(JNIEnv *env, job
     auto profile = ptrToProfile(env, thiz);
     auto pic = util::deserialize_user_pic(env, user_pic);
     auto url = env->GetStringUTFChars(pic.first, nullptr);
-    auto key = util::ustring_from_bytes(env, pic.second);
+    auto key = util::vector_from_bytes(env, pic.second);
     profile->set_profile_pic(url, key);
     env->ReleaseStringUTFChars(pic.first, url);
 }
diff --git a/libsession-util/src/main/cpp/util.cpp b/libsession-util/src/main/cpp/util.cpp
index 70979c4ca5..dffcfc349e 100644
--- a/libsession-util/src/main/cpp/util.cpp
+++ b/libsession-util/src/main/cpp/util.cpp
@@ -2,6 +2,7 @@
 #include "sodium/randombytes.h"
 #include <sodium/crypto_sign.h>
 #include <session/multi_encrypt.hpp>
+#include <session/util.hpp>
 #include <string>
 
 #include <android/log.h>
@@ -17,26 +18,35 @@ namespace util {
 
     std::mutex util_mutex_ = std::mutex();
 
-    jbyteArray bytes_from_ustring(JNIEnv* env, session::ustring_view from_str) {
-        size_t length = from_str.length();
+    jbyteArray bytes_from_vector(JNIEnv* env, std::vector<unsigned char> from_str) {
+        size_t length = from_str.size();
         auto jlength = (jsize)length;
         jbyteArray new_array = env->NewByteArray(jlength);
         env->SetByteArrayRegion(new_array, 0, jlength, (jbyte*)from_str.data());
         return new_array;
     }
 
-    session::ustring ustring_from_bytes(JNIEnv* env, jbyteArray byteArray) {
+    std::vector<unsigned char> vector_from_bytes(JNIEnv* env, jbyteArray byteArray) {
         if (byteArray == nullptr) {
             return {};
         }
         size_t len = env->GetArrayLength(byteArray);
         auto bytes = env->GetByteArrayElements(byteArray, nullptr);
 
-        session::ustring st{reinterpret_cast<const unsigned char *>(bytes), len};
+        auto begin = reinterpret_cast<const unsigned char *>(bytes);
+        std::vector<unsigned char> st{begin, begin + len};
         env->ReleaseByteArrayElements(byteArray, bytes, 0);
         return st;
     }
 
+    jbyteArray bytes_from_span(JNIEnv* env, std::span<const unsigned char> from_str) {
+        size_t length = from_str.size();
+        auto jlength = (jsize)length;
+        jbyteArray new_array = env->NewByteArray(jlength);
+        env->SetByteArrayRegion(new_array, 0, jlength, (jbyte*)from_str.data());
+        return new_array;
+    }
+
     std::string string_from_jstring(JNIEnv* env, jstring string) {
         size_t len = env->GetStringUTFLength(string);
         auto chars = env->GetStringUTFChars(string, nullptr);
@@ -50,7 +60,7 @@ namespace util {
         jclass returnObjectClass = env->FindClass("network/loki/messenger/libsession_util/util/UserPic");
         jmethodID constructor = env->GetMethodID(returnObjectClass, "<init>", "(Ljava/lang/String;[B)V");
         jstring url = env->NewStringUTF(pic.url.data());
-        jbyteArray byteArray = util::bytes_from_ustring(env, pic.key);
+        jbyteArray byteArray = util::bytes_from_vector(env, pic.key);
         return env->NewObject(returnObjectClass, constructor, url, byteArray);
     }
 
@@ -202,14 +212,14 @@ JNIEXPORT jobject JNICALL
 Java_network_loki_messenger_libsession_1util_util_Sodium_ed25519KeyPair(JNIEnv *env, jobject thiz, jbyteArray seed) {
     std::array<unsigned char, 32> ed_pk; // NOLINT(cppcoreguidelines-pro-type-member-init)
     std::array<unsigned char, 64> ed_sk; // NOLINT(cppcoreguidelines-pro-type-member-init)
-    auto seed_bytes = util::ustring_from_bytes(env, seed);
+    auto seed_bytes = util::vector_from_bytes(env, seed);
     crypto_sign_ed25519_seed_keypair(ed_pk.data(), ed_sk.data(), seed_bytes.data());
 
     jclass kp_class = env->FindClass("network/loki/messenger/libsession_util/util/KeyPair");
     jmethodID kp_constructor = env->GetMethodID(kp_class, "<init>", "([B[B)V");
 
-    jbyteArray pk_jarray = util::bytes_from_ustring(env, session::ustring_view {ed_pk.data(), ed_pk.size()});
-    jbyteArray sk_jarray = util::bytes_from_ustring(env, session::ustring_view {ed_sk.data(), ed_sk.size()});
+    jbyteArray pk_jarray = util::bytes_from_span(env, std::span<const unsigned char> {ed_pk.data(), ed_pk.size()});
+    jbyteArray sk_jarray = util::bytes_from_span(env, std::span<const unsigned char> {ed_sk.data(), ed_sk.size()});
 
     jobject return_obj = env->NewObject(kp_class, kp_constructor, pk_jarray, sk_jarray);
     return return_obj;
@@ -220,7 +230,7 @@ JNIEXPORT jbyteArray JNICALL
 Java_network_loki_messenger_libsession_1util_util_Sodium_ed25519PkToCurve25519(JNIEnv *env,
                                                                                jobject thiz,
                                                                                jbyteArray pk) {
-    auto ed_pk = util::ustring_from_bytes(env, pk);
+    auto ed_pk = util::vector_from_bytes(env, pk);
     std::array<unsigned char, 32> curve_pk; // NOLINT(cppcoreguidelines-pro-type-member-init)
     int success = crypto_sign_ed25519_pk_to_curve25519(curve_pk.data(), ed_pk.data());
     if (success != 0) {
@@ -228,7 +238,7 @@ Java_network_loki_messenger_libsession_1util_util_Sodium_ed25519PkToCurve25519(J
         env->ThrowNew(exception, "Invalid crypto_sign_ed25519_pk_to_curve25519 operation");
         return nullptr;
     }
-    jbyteArray curve_pk_jarray = util::bytes_from_ustring(env, session::ustring_view {curve_pk.data(), curve_pk.size()});
+    jbyteArray curve_pk_jarray = util::bytes_from_span(env, std::span<const unsigned char> {curve_pk.data(), curve_pk.size()});
     return curve_pk_jarray;
 }
 
@@ -243,26 +253,26 @@ Java_network_loki_messenger_libsession_1util_util_Sodium_encryptForMultipleSimpl
         env->ThrowNew(env->FindClass("java/lang/IllegalArgumentException"), "Messages and recipients must be the same size");
         return nullptr;
     }
-    std::vector<session::ustring> message_vec{};
-    std::vector<session::ustring> recipient_vec{};
+    std::vector<std::vector<unsigned char>> message_vec{};
+    std::vector<std::vector<unsigned char>> recipient_vec{};
     for (int i = 0; i < size; i++) {
         jbyteArray message_j = static_cast<jbyteArray>(env->GetObjectArrayElement(messages, i));
         jbyteArray recipient_j = static_cast<jbyteArray>(env->GetObjectArrayElement(recipients, i));
-        session::ustring message = util::ustring_from_bytes(env, message_j);
-        session::ustring recipient = util::ustring_from_bytes(env, recipient_j);
+        std::vector<unsigned char> message = util::vector_from_bytes(env, message_j);
+        std::vector<unsigned char> recipient = util::vector_from_bytes(env, recipient_j);
 
-        message_vec.emplace_back(session::ustring{message});
-        recipient_vec.emplace_back(session::ustring{recipient});
+        message_vec.emplace_back(message);
+        recipient_vec.emplace_back(recipient);
     }
 
-    std::vector<session::ustring_view> message_sv_vec{};
-    std::vector<session::ustring_view> recipient_sv_vec{};
+    std::vector<std::span<const unsigned char>> message_sv_vec{};
+    std::vector<std::span<const unsigned char>> recipient_sv_vec{};
     for (int i = 0; i < size; i++) {
-        message_sv_vec.emplace_back(session::to_unsigned_sv(message_vec[i]));
-        recipient_sv_vec.emplace_back(session::to_unsigned_sv(recipient_vec[i]));
+        message_sv_vec.emplace_back(session::to_span(message_vec[i]));
+        recipient_sv_vec.emplace_back(session::to_span(recipient_vec[i]));
     }
 
-    auto sk = util::ustring_from_bytes(env, ed25519_secret_key);
+    auto sk = util::vector_from_bytes(env, ed25519_secret_key);
     std::array<unsigned char, 24> random_nonce;
     randombytes_buf(random_nonce.data(), random_nonce.size());
 
@@ -273,11 +283,11 @@ Java_network_loki_messenger_libsession_1util_util_Sodium_encryptForMultipleSimpl
             recipient_sv_vec,
             sk,
             domain_string,
-            session::ustring_view {random_nonce.data(), 24}
+            std::span<const unsigned char> {random_nonce.data(), 24}
     );
 
     env->ReleaseStringUTFChars(domain, domain_string);
-    auto encoded = util::bytes_from_ustring(env, result);
+    auto encoded = util::bytes_from_vector(env, result);
     return encoded;
 }
 
@@ -289,19 +299,19 @@ Java_network_loki_messenger_libsession_1util_util_Sodium_decryptForMultipleSimpl
                                                                                   jbyteArray secret_key,
                                                                                   jbyteArray sender_pub_key,
                                                                                   jstring domain) {
-    auto sk_ustring = util::ustring_from_bytes(env, secret_key);
-    auto encoded_ustring = util::ustring_from_bytes(env, encoded);
-    auto pub_ustring = util::ustring_from_bytes(env, sender_pub_key);
+    auto sk_vector = util::vector_from_bytes(env, secret_key);
+    auto encoded_vector = util::vector_from_bytes(env, encoded);
+    auto pub_vector = util::vector_from_bytes(env, sender_pub_key);
     auto domain_bytes = env->GetStringUTFChars(domain, nullptr);
     auto result = session::decrypt_for_multiple_simple(
-            encoded_ustring,
-            sk_ustring,
-            pub_ustring,
+            encoded_vector,
+            sk_vector,
+            pub_vector,
             domain_bytes
             );
     env->ReleaseStringUTFChars(domain,domain_bytes);
     if (result) {
-        return util::bytes_from_ustring(env, *result);
+        return util::bytes_from_vector(env, *result);
     } else {
         LOGD("no result from decrypt");
     }
@@ -321,7 +331,7 @@ Java_network_loki_messenger_libsession_1util_util_BaseCommunityInfo_00024Compani
 
     auto base_j = env->NewStringUTF(base.data());
     auto room_j = env->NewStringUTF(room.data());
-    auto pk_jbytes = util::bytes_from_ustring(env, pk);
+    auto pk_jbytes = util::bytes_from_vector(env, pk);
 
     jobject triple = env->NewObject(clazz, constructor, base_j, room_j, pk_jbytes);
     return triple;
diff --git a/libsession-util/src/main/cpp/util.h b/libsession-util/src/main/cpp/util.h
index 234ceb0017..7c884dfe6c 100644
--- a/libsession-util/src/main/cpp/util.h
+++ b/libsession-util/src/main/cpp/util.h
@@ -4,6 +4,8 @@
 #include <jni.h>
 #include <array>
 #include <optional>
+#include <span>
+#include <vector>
 #include "session/types.hpp"
 #include "session/config/groups/info.hpp"
 #include "session/config/groups/keys.hpp"
@@ -14,8 +16,9 @@
 
 namespace util {
     extern std::mutex util_mutex_;
-    jbyteArray bytes_from_ustring(JNIEnv* env, session::ustring_view from_str);
-    session::ustring ustring_from_bytes(JNIEnv* env, jbyteArray byteArray);
+    jbyteArray bytes_from_vector(JNIEnv* env, std::vector<unsigned char> from_str);
+    std::vector<unsigned char> vector_from_bytes(JNIEnv* env, jbyteArray byteArray);
+    jbyteArray bytes_from_span(JNIEnv* env, std::span<const unsigned char> from_str);
     std::string string_from_jstring(JNIEnv* env, jstring string);
     jobject serialize_user_pic(JNIEnv *env, session::config::profile_pic pic);
     std::pair<jstring, jbyteArray> deserialize_user_pic(JNIEnv *env, jobject user_pic);