security: Add ed25519 signer

[zjkmxy]

Fix: #91

[zjkmxy]

Validator is already there

ndnd/std/security/known-key-validator.go

Lines 72 to 80 in be1788d

	// EddsaValidate verifies the signature with a known ed25519 public key.
	// ndn-cxx's PIB does not support this, but a certificate is supposed to use ASN.1 DER format.
	// Use x509.ParsePKIXPublicKey to parse. Note: ed25519.PublicKey is defined to be a pointer type without '*'.
	func EddsaValidate(sigCovered enc.Wire, sig ndn.Signature, pubKey ed25519.PublicKey) bool {
	if sig.SigType() != ndn.SignatureEd25519 {
	return false
	}
	return ed25519.Verify(pubKey, sigCovered.Join(), sig.SigValue())
	}

Don't have a unit test for now (WIP), but it should work.

[yoursunny]

Need test cases:

• Sign then verify.
• Import the public key from a self-signed Ed25519 certificate and verify the certificate packet. The sample certificate is linked from Ed25519 signature type #91 (comment)

[zjkmxy]

I have not finished addressing Junxiao's comments but thank Varun for reviewing.
Please do not merge for now :)

[Pesa]

nitpicking on the naming: "ECC" is a very broad category of cryptography but this code is specifically for ECDSA. Saying "ecc signing" or "ecc key" is fairly meaningless (what algorithm?). Moreover, EdDSA also uses elliptic curves (twisted Edwards curves), so this naming could be confusing. The comment above is also meaningless for similar reasons.

[Pesa]

also nitpicking but much less important than the previous comment: EdDSA can be instantiated with different curves and hash algorithms. Ed25519 is just one instance (arguably the most common one) but the name edSigner could potentially indicate that this is for EdDSA generically. Thankfully, the comment is clear that it's for Ed25519, so this is not too important at the end of the day. It could become awkward when/if we introduce the Ed448 signature type.