Подпись файла с использованием FileAPI

<script language="javascript" src="cadesplugin_api.js"></script>

        function SignCreate(certSubjectName, dataToSign) {
            var oStore = cadesplugin.CreateObject("CAdESCOM.Store");
            oStore.Open(cadesplugin.CAPICOM_CURRENT_USER_STORE, cadesplugin.CAPICOM_MY_STORE,
                cadesplugin.CAPICOM_STORE_OPEN_MAXIMUM_ALLOWED);

            var oCertificates = oStore.Certificates.Find(
                cadesplugin.CAPICOM_CERTIFICATE_FIND_SUBJECT_NAME, certSubjectName);
            if (oCertificates.Count == 0) {
                alert("Certificate not found: " + certSubjectName);
                return;
            }
            var oCertificate = oCertificates.Item(1);
            var oSigner = cadesplugin.CreateObject("CAdESCOM.CPSigner");
            oSigner.Certificate = oCertificate;
            oSigner.CheckCertificate = true;

            var oSignedData = cadesplugin.CreateObject("CAdESCOM.CadesSignedData");
            oSignedData.ContentEncoding = cadesplugin.CADESCOM_BASE64_TO_BINARY;
            oSignedData.Content = dataToSign;

            try {
                var sSignedMessage = oSignedData.SignCades(oSigner, cadesplugin.CADESCOM_CADES_BES, true);
            } catch (err) {
                alert("Failed to create signature. Error: " + cadesplugin.getLastError(err));
                return;
            }

            oStore.Close();

            return sSignedMessage;
        }

        function Verify(sSignedMessage, dataToVerify) {
            var oSignedData = cadesplugin.CreateObject("CAdESCOM.CadesSignedData");
            try {
                oSignedData.ContentEncoding = cadesplugin.CADESCOM_BASE64_TO_BINARY;
                oSignedData.Content = dataToVerify;
                oSignedData.VerifyCades(sSignedMessage, cadesplugin.CADESCOM_CADES_BES, true);
            } catch (err) {
                alert("Failed to verify signature. Error: " + cadesplugin.getLastError(err));
                return false;
            }

            return true;
        }

        function run() {
            // Проверяем, работает ли File API
            if (window.FileReader) {
                // Браузер поддерживает File API.
            } else {
                alert('The File APIs are not fully supported in this browser.');
            }
            if (0 == document.getElementById("uploadFile").files.length) {
                alert("Select the file.");
                return;
            }
            var oFile = document.getElementById("uploadFile").files[0];
            var oFReader = new FileReader();

            if (typeof(oFReader.readAsDataURL)!="function") {
                alert("Method readAsDataURL() is not supported in FileReader.");
                return;
            }

            oFReader.readAsDataURL(oFile);

            oFReader.onload = function(oFREvent) {
                var header = ";base64,";
                var sFileData = oFREvent.target.result;
                var sBase64Data = sFileData.substr(sFileData.indexOf(header) + header.length);

                var oCertName = document.getElementById("CertName");
                var sCertName = oCertName.value; // Здесь следует заполнить SubjectName сертификата
                if ("" == sCertName) {
                    alert("Введите имя сертификата (CN).");
                    return;
                }
                var signedMessage = SignCreate(sCertName, sBase64Data);

                // Выводим отделенную подпись в BASE64 на страницу
                // Такая подпись должна проверяться в КриптоАРМ и cryptcp.exe
                document.getElementById("signature").innerHTML = signedMessage;

                var verifyResult = Verify(signedMessage, sBase64Data);
                if (verifyResult) {
                    alert("Signature verified");
                }
            };
        }