tunnel: clean up some docstring wording

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

tunnel/src/main/java/com/wireguard/crypto/Curve25519.java

@@ -13,7 +13,7 @@ import java.util.Arrays;
 import androidx.annotation.Nullable;
 
 /**
- * Implementation of the Curve25519 elliptic curve algorithm.
+ * Implementation of Curve25519 ECDH.
  * <p>
  * This implementation was imported to WireGuard from noise-java:
  * https://github.com/rweather/noise-java

tunnel/src/main/java/com/wireguard/crypto/Ed25519.java

@@ -13,7 +13,9 @@ import java.security.MessageDigest;
 import java.util.Arrays;
 
 /**
- * This implementation is based on the ed25519/ref10 implementation in NaCl.
+ * Implementation of Ed25519 signature verification.
+ *
+ * <p>This implementation is based on the ed25519/ref10 implementation in NaCl.</p>
  *
  * <p>It implements this twisted Edwards curve:
  *