PHPECC vulnerable to multiple cryptographic side-channel attacks

Summary

### ECDSA Canonicalization PHPECC is vulnerable to malleable ECDSA signature attacks. ### Constant-Time Signer When generating a new ECDSA signature, the GMPMath adapter was used. This class wraps the GNU Multiple Precision arithmetic library (GMP), which does not aim to provide constant-time implementations of algorithms. An attacker capable of triggering many signatures and studying the time it takes to perform each operation would be able to leak the secret number, `k`, and thereby learn the private key. ### EcDH Timing Leaks When calculating a shared secret using the `EcDH` class, the scalar-point multiplication is based on the arithmetic defined by the `Point` class. Even though the library implements a Montgomery ladder, the `add()`, `mul()`, and `getDouble()` methods on the `Point` class are not constant-time. This means that your ECDH private keys are leaking information about each bit of your private key through a timing side-channel.