Document and simplify library usage

Makefile

@@ -1,6 +1,6 @@
 CC = /usr/bin/gcc
 CFLAGS = -Wall -g -O3 -Wextra -Wpedantic
-LDLIBS =  -lcrypto -lm
+LDLIBS =  -lcrypto
 
 SOURCES = params.c hash.c fips202.c hash_address.c randombytes.c wots.c xmss.c xmss_core.c xmss_commons.c
 HEADERS = params.h hash.h fips202.h hash_address.h randombytes.h wots.h xmss.h xmss_core.h xmss_commons.h
@@ -34,7 +34,7 @@ test/%: test/%.c $(SOURCES) $(OBJS) $(HEADERS)
 	$(CC) $(CFLAGS) -o $@ $(SOURCES) $< $(LDLIBS)
 
 test/test_wots: params.c hash.c fips202.c hash_address.c randombytes.c wots.c xmss_commons.c test/test_wots.c params.h hash.h fips202.h hash_address.h randombytes.h wots.h xmss_commons.h
-	$(CC) $(CFLAGS) params.c hash.c fips202.c hash_address.c randombytes.c wots.c xmss_commons.c test/test_wots.c -o $@ -lcrypto -lm
+	$(CC) $(CFLAGS) params.c hash.c fips202.c hash_address.c randombytes.c wots.c xmss_commons.c test/test_wots.c -o $@ -lcrypto
 
 clean:
 	-$(RM) $(TESTS)

README.md

@@ -8,6 +8,10 @@ _While the behavior of the code in this repository is supposed to be stable, the
 
 _When using the current code base, please be careful, expect changes and watch this document for further documentation._
 
+### Dependencies
+
+For the SHA-2 hash functions (i.e. SHA-256 and SHA-512), we rely on OpenSSL. Make sure to install the OpenSSL development headers. On Debian-based systems, this is achieved by installing the OpenSSL development package `libssl-dev`.
+
 ### License
 
 This reference implementation was written by Andreas Hülsing and Joost Rijneveld. All included code is available under the CC0 1.0 Universal Public Domain Dedication.

test/test_wots.c

@@ -1,5 +1,4 @@
 #include <stdio.h>
-#include <math.h>
 #include <stdint.h>
 #include "../wots.h"
 #include "../randombytes.h"