Add README and CHANGELOG

CHANGELOG

@@ -0,0 +1,15 @@
+libuecc v6 (in development)
+
+* Fixes a bug which might have caused a point's y coordinate to be negated
+    in certain circumstances when the point was stored in packed
+    representation and loaded again. It is extremely improbable that this
+    has ever actually happened, as only a small range of coordinates was
+    affected.
+* Use stdint types to clarify ABI and add support for systems with
+    sizeof(int) < 4 (this is not an ABI break in practise as all systems on
+    which libuecc has been used in the past should have int == int32_t)
+* Add point negation and subtraction functions
+* Rename all point access functions to bear a _legacy suffix (the old names
+    are still available, but marked as deprecated)
+* Add new point access functions and a new generator point that are
+    compatible with Ed25519

README

@@ -0,0 +1,30 @@
+libuecc is a very small generic-purpose Elliptic Curve Cryptography library
+compatible with Ed25519.
+
+Most documentation can be found as Doxygen comments in the ecc.h header
+file. You can use `make doxygen` after running CMake to create HTML
+documenation from it.
+
+There are two sets of functions converting between libuecc's internal point
+representation and coordinates or compressed representation. The functions
+ending with _ed25519 use the same representation as original Ed25519
+implementation and should be used by new software. The functions with the
+suffix _legacy are provided for compatiblity with libuecc version before
+v6.
+
+Ed25519 and the legacy representation are isomorphic, they use a Twisted
+Edwards Curve
+
+    ax^2 + y^2 = 1 + dx^2y^2
+
+over the prime field for p = 2^255 - 19.
+
+Ed25519 uses the parameters
+
+    a = -1 and
+    d = -(121665/121666),
+
+while the legacy curve has
+
+    a = 486664
+    d = 486660.