Update README on E2EE

[skip ci]

1 files changed, 32 insertions, 11 deletions

diff --git a/README.md b/README.md
index 6278535a..e7597fce 100644
--- a/README.md
+++ b/README.md
@@ -30,8 +30,8 @@ in SECURITY.md.
 
 ## Getting and using libQuotient
 Depending on your platform, the library can be obtained from a package
-management system. Recent releases of Debian and openSUSE, e.g., already have
-it. Alternatively, just build the library from the source and bundle it with
+management system. Recent releases of Fedora, Debian and openSUSE already have
+it. Alternatively, you can build the library from the source and bundle it with
 your application, as described below.
 
 ### Pre-requisites
@@ -39,12 +39,16 @@ your application, as described below.
   mobile operating systems where Qt is available might work too)
   - Recent enough Linux examples: Debian Bullseye; Fedora 35;
     openSUSE Leap 15.4; Ubuntu 22.04 LTS.
-- Qt 5 (either Open Source or Commercial), 5.15 or higher
-- CMake 3.16 or newer (from your package management system or
-  [the official website](https://cmake.org/download/))
-- A C++ toolchain with that supports at least some subset of C++20:
+- Qt 5.15 or 6 (experimental, as of libQuotient 0.7) - either Open Source or
+  Commercial
+- CMake 3.16 or newer
+- A C++ toolchain that supports at least some subset of C++20 (concepts,
+  in particular):
   - GCC 11 (Windows, Linux, macOS), Clang 11 (Linux), Apple Clang 12 (macOS)
     and Visual Studio 2019 (Windows) are the oldest officially supported.
+- If using E2EE (beta, as of libQuotient 0.7):
+  - libolm 3.x (the latest 3.x strongly recommended)
+  - OpenSSL (1.1.x is known to work; 3.x should likely work too).
 - Any build system that works with CMake should be fine:
   GNU Make and ninja on any platform, NMake and jom on Windows are known to work.
   Ninja is recommended.
@@ -56,8 +60,11 @@ at error messages. The library is entirely offscreen but aside from QtCore and
 QtNetwork it also depends on QtGui in order to handle avatar thumbnails.
 
 #### macOS
-`brew install qt5` should get you a recent Qt5. You may need to pass
-`-DCMAKE_PREFIX_PATH=$(brew --prefix qt5)` to make it aware of the Qt location.
+`brew install qt5` should get you a recent Qt5. You may need to add the output
+of `brew --prefix qt5` to `CMAKE_PREFIX_PATH` (see below) to make CMake aware
+of the Qt location.
+
+If using E2EE, you need to perform the same dance for libolm and openssl.
 
 #### Windows
 Install Qt5 using their official installer; make sure to tick the CMake box
@@ -72,6 +79,14 @@ on system startup but it's very handy to setup the environment before building.
 Alternatively you can add the Qt path to `CMAKE_PREFIX_PATH` and leave PATH
 unchanged.
 
+If you're trying out E2EE, you will also need libolm and OpenSSL. Unfortunately,
+neither project provides official binary libraries for Windows. libolm can
+be compiled from the sources (available at ) using the same toolchain
+(CMake+MSVC). It's not recommended to compile OpenSSL yourself; instead, use
+one of the "OpenSSL for Windows" links in
+[unofficial list on the project Wiki](https://wiki.openssl.org/index.php/Binaries).
+
+
 ### Using the library
 If you're just starting a project using libQuotient from scratch, you can copy
 `quotest/CMakeLists.txt` to your project and change `quotest` to your
@@ -121,6 +136,9 @@ Static builds are tested on all supported platforms, building the library as
 a shared object (aka dynamic library) is supported on Linux and macOS but is
 very likely to be broken on Windows.
 
+Before proceeding, double-check that you have installed development libraries
+for all prerequisites above. CMake will stop and tell you if something's missing.
+
 The first CMake invocation above configures the build. You can pass CMake
 variables (such as `-DCMAKE_PREFIX_PATH="path1;path2;..."` and
 `-DCMAKE_INSTALL_PREFIX=path`) here if needed.
@@ -137,11 +155,14 @@ the standard variables coming with CMake. On top of them, Quotient introduces:
   to get the contents of `#quotient:matrix.org`; this is being fixed in
   [#401](https://github.com/quotient-im/libQuotient/issues/401).
 - `Quotient_ENABLE_E2EE=<ON/OFF>`, `OFF` by default - enable work-in-progress
-  E2EE code in the library. As of 0.6, this code is very incomplete and leaks
-  memory; only set this to `ON` if you want to help making this code work.
+  E2EE code in the library. As of 0.6, this code is very incomplete and buggy;
+  you should NEVER use it. In 0.7, the enabled code is beta-quality and is
+  generally good for trying the technology and API but really not for
+  mission-critical applications.
+
   Switching this on will define `Quotient_E2EE_ENABLED` macro (note
   the difference from the CMake switch) for compiler invocations on all
-  Quotient and Quotient-dependent (if it uses `find_package(Quotient 0.6)`)
+  Quotient and Quotient-dependent (if it uses `find_package(Quotient)`)
   code; so you can use `#ifdef Quotient_E2EE_ENABLED` to guard the code using
   E2EE parts of Quotient.
 - `MATRIX_SPEC_PATH` and `GTAD_PATH` - these two variables are used to point