Ответ 1
Вы можете использовать SHA256.Create()
(от System.Security.Cryptography.Algorithms
):
using (var algorithm = SHA256.Create())
{
// Create the at_hash using the access token returned by CreateAccessTokenAsync.
var hash = algorithm.ComputeHash(Encoding.ASCII.GetBytes(response.AccessToken));
// Note: only the left-most half of the hash of the octets is used.
// See http://openid.net/specs/openid-connect-core-1_0.html#CodeIDToken
identity.AddClaim(JwtRegisteredClaimNames.AtHash, Base64UrlEncoder.Encode(hash, 0, hash.Length / 2));
}