Letterbook.NSign.SignatureProviders 0.19.1

NSign.SignatureProviders

Signature providers for signing and verifying signatures with NSign. This library currently supports both asymmetric algorithms (using public-key cryptography) and symmetric algorithms (using HMAC). Signature providers typically implement both the ISigner and the IVerifier interfaces, but implementation can also be split into separate classes.

Asymmetric Signature Algorithms

Currently, the following asymmetrics signature algorithms are supported:

• ECDSA using curve P-256 DSS and SHA-256 (ecdsa-p256-sha256 in [^1]), in class ECDsaP256Sha256SignatureProvider
• ECDSA using curve P-384 DSS and SHA-384 (ecdsa-p384-sha384 in [^1]), in class ECDsaP382Sha384SignatureProvider
• RSASSA-PSS using SHA-512 (rsa-pss-sha512 in [^1]) in class RsaPssSha512SignatureProvider
• RSASSA-PKCS1-v1_5 using SHA-256 (rsa-v1_5-sha256 in [^1]) in class RsaPkcs15Sha256SignatureProvider

These signature providers can all be created by passing an instance of X509Certificate2 and having the provider extract the public key for signature verification from there. If the provider is to be used for signing, the certificate that is provided must have a private key too, otherwise signing will fail / an exception will be thrown. Naturally, the keys used in the certificate must match the key parameters/formats expected by the signature provider.

For instance, to use rsa-pss-sha512 with a PEM-encoded certificate in a file called the-cert.cer for signature verification, creating the provider as follows will do:

var provider = new RsaPssSha512SignatureProvider(
	new X509Certificate2("the-cert.cer"),
	"the-cert-key-id"))

To use rsa-pss-sha512 with a PFX file called the-cert.pfx, holding the private key for message signing, a provider can be created as follows:

var provider = new RsaPssSha512SignatureProvider(
	new X509Certificate2("the-cert.pfx", "here-goes-the-password-to-the-PFX"),
	"the-cert-key-id"))

Due to their nature, asymmetric signatures are often preferable over symmetric signatures because they do not require both the signing and verifying party to share a secret (the key). Instead, the public key can be published anywhere / through any means for verifiers to download and use.

Symmetric Signature Algorithms

Currently, the following symmetric signature algorithms are supported:

• HMAC using SHA-256 (hmac-sha256 in [^1]), in class HmacSha256SignatureProvider

This signature provider requires the (shared) key to be provided during construction.

Further Information

See also:

• NSign on github.com
• HTTP Message Signatures (current draft)

[^1]: See section Signature Algorithms of HTTP Message Signatures, https://datatracker.ietf.org/doc/draft-ietf-httpbis-message-signatures/