/// <summary>
/// Searches the specified text for a signature block.
/// If found it is verified that is belongs to the text,
/// which indicates that the text has not been modified.
/// </summary>
/// <param name="signer">The <see cref="ISigner"/>
/// instance that is used to generate the signature.</param>
/// <param name="text">The text which contains an embedded signature.</param>
/// <param name="publicKey">The public key for verifying the signature.</param>
/// <returns>A <see cref="TextVerificationResult"/> indicating
/// whether the signature is valid or not. If the text does
/// not contain an embedded signature, <c>SignatureVerified</c>
/// is set to <c>false</c>. The <c>TextVerificationResult</c>
/// object also contains the text without the signature.</returns>
/// <exception cref="ArgumentNullException">
/// Occurs if any of the arguments are null.</exception>
public async Task <TextVerificationResult> VerifySignatureAsync(
ISigner signer, string text, string publicKey)
{
AssertArg.IsNotNull(signer, nameof(signer));
AssertArg.IsNotNull(text, nameof(text));
AssertArg.IsNotNull(publicKey, nameof(publicKey));
var regex = GetSignatureRegex();
var match = regex.Match(text);
if (!match.Success)
{
return(new TextVerificationResult(false, null));
}
var signatureText = match.Groups["Signature"].Value;
var allText = match.Groups["All"].Value;
string withoutSignature = text.Replace(allText, string.Empty);
bool result = await signer.VerifyBase64SignatureAsync(
withoutSignature, signatureText, publicKey, Encoding);
return(new TextVerificationResult(result, withoutSignature));
}
