sign: function (data, certificate) {
        try {
            var signer = this.createCryptoObject(this.getSignerString());
        }
        catch (e) {
            this.alert('Ошибка', 'Ошибка получения объекта для подписания: ' + e.message);
            return null;
        }

        if (signer && certificate) {
            signer.Certificate = certificate;
        }
        else {
            this.alert('Ошибка', 'Не удалось получить сертификато либо объект для подписания');
        }

        var signedData = this.createCryptoObject(this.getSignedDataString());

        if (!this.isIE()) {
            signedData.ContentEncoding = this.constants.cryptoPro.CADESCOM_BASE64_TO_BINARY;
        }

        signedData.Content = data;

        try {
            var signature = this.isIE() ?
                signedData.Sign(signer, true /*detached*/, this.constants.encodingType.CAPICOM_ENCODE_BASE64)
                : signedData.SignCades(signer, this.constants.cryptoPro.CADES_BES, true /*detached*/, this.constants.encodingType.CAPICOM_ENCODE_BASE64);
            return signature;
        }
        catch (e) {
            this.alert('Ошибка подписания документа: ' + e.message);
            return null;
        }
    }

Проверка:
verify: function (signed, detached, content) {
        var signedData = this.createCryptoObject(this.getSignedDataString());
        if (detached) {
            signedData.Content = content;
        }

        if (this.isIE()) {
            try {
                signedData.Verify(signed, detached, this.constants.verifyFlag.CAPICOM_VERIFY_SIGNATURE_ONLY);
                return true;
            }
            catch (e) {
                return false;
            }
        }
        else {
            try {
                signedData.ContentEncoding = this.constants.cryptoPro.CADESCOM_BASE64_TO_BINARY;
                signedData.VerifyCades(signed, this.constants.cryptoPro.CADES_BES, detached);
                return true;
            }
            catch (e) {
                return false;
            }
        }
    }