Improve README.md and BUILDIND.md.

Author: briansmith

BUILDING.md

@@ -15,6 +15,12 @@ msbuild projects (on Windows) or the Makefile (on other platforms). Because
 this is a little unusual, I would be particularly grateful if you could report
 any problems building (or using) *ring*'s Rust crate.
 
+Currently on Windows you must currently invoke cargo from a Visual Studio
+Native Tools Command Prompt. Otherwise the build will likely fail in confusing
+ways because either msbuild won't be found or there will be a version mismatch
+between the toolchain used to build the C parts of the library and the toolchain
+used by cargo/rustc for linking.
+
 
 
 Building the C Library on Linux and Similar Platforms

README.md

@@ -11,15 +11,13 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 What is *ring*?
 ===============
 
-*ring* is a simplified version of BoringSSL with C and Rust APIs.
+*ring* is a crypto library in Rust based on BoringSSL's crypto primitive
+implementations.
 
-*ring* makes OpenSSL's high-quality, high-performance crypto primitives
-conveniently available to new crypto libraries written in safer (than C)
-languages like OCaml and Rust. Particular attention is being paid to making it
-easy to build and integrate *ring* into applications and higher-level
-frameworks, and to ensuring that *ring* works optimally on microcontrollers
-to support Internet of Things (IoT) applications. It may also be useful for
-people implementing cryptographic protocols in C and C++.
+Particular attention is being paid to making it easy to build and integrate
+*ring* into applications and higher-level frameworks, and to ensuring that
+*ring* works optimally on microcontrollers to support Internet of Things
+(IoT) applications.
 
 The name *ring* comes from the fact that *ring* started as a subset of
 BoringSSL, and *"ring"* is a substring of "Bo*ring*SSL". Almost all the code in
@@ -37,25 +35,32 @@ The first part of the ```ring``` Rust crate is now available.
 
 Currently these features are supported through the Rust API:
 
-* Cryptographic digests (SHA-256, SHA-384, SHA-512, SHA-1, and MD5).
-* HMAC.
-* ECDSA Signature Verification for curves P-256, P-384, and P-521.
-* RSA PKCS#1 Signature Verification.
-* Random byte generation.
+* Cryptographic digests (SHA-256, SHA-384, SHA-512, SHA-1, and MD5)
+* HMAC, HKDF, and PBKDF2-HMAC
+* Ephemeral ECDH key agreement for curves P-256, P-384, and P-521
+* ECDSA signature verification for curves P-256, P-384, and P-521
+* RSA PKCS#1 signature verification
+* Random byte generation
 
 See the documentation at
 https://briansmith.org/rustdoc/ring/. Also take a look at the example
-program [checkdigest.rs](examples/checkdigest.rs).
+program [examples/checkdigest.rs](examples/checkdigest.rs).
 
 See [Building the Rust Library](BUILDING.md#building-the-rust-library) for
-instructions on how to build it (hint: it's just ```cargo build```).
+instructions on how to build it.
 
 
 
 The C API
 =========
-The C API is the same as BoringSSL's, except that its SSL/TLS, X.509, and
-ASN.1 APIs have been removed. See
+The C API is the same as BoringSSL's, except that its SSL/TLS, X.509,
+ASN.1 APIs, error stack mechanism, and many parts of the EVP interface have
+been permanently removed. Currently, the C API also does not expose HMAC, HKDF,
+and PBKDF2 because the C wrappers around the new Rust implementations have not
+been implemented yet. The currently plan is to support a C interface that is
+the same as or similar to BoringSSL's.
+
+See
 [this](https://github.com/briansmith/ring/blob/master/BUILDING.md#building-the-c-library-on-windows)
 (for Windows) and
 [this](https://github.com/briansmith/ring/blob/master/BUILDING.md#building-the-c-library-on-linux-and-similar-platforms)
@@ -69,15 +74,20 @@ Contributing
 
 Patches Welcome! Suggestions:
 
+* More code elimination, especially dead code.
+* Replacing more C code with Rust code.
+* Implementation of [SRP-6a](http://srp.stanford.edu/) in Rust, based on the
+  |rust::digest| API and the C/asm optimized modular exponentiation.
+* Optimizing the PBKDF2-HMAC implementation based on the ideas from
+  [fastpbkdf2](https://github.com/ctz/fastpbkdf2).
+* X25519 (ECDH with Curve25519) and Ed25519.
 * Better IDE support for Windows (e.g. running the tests within the IDE) and
   Mac OS X (e.g. Xcode project files).
 * Language bindings for safer programming languages like Haskell, OCaml, and
   Rust.
 * Support for more platforms in the continuous integration, such as Android,
   Mac OS X, and ARM microcontrollers. (The current CI only covers Linux.)
 * Static analysis and fuzzing in the continuous integration.
-* More code elimination, especially dead code.
-
 
 
 License