XmlDocument document = GetDocument();
X509Certificate2 clientCertificate = GetCertificate();

SignedXml signedDoc = new SignedXml(document);
Reference reference = new Reference();
reference.Uri = "#signed";
reference.DigestMethod = CPSignedXml.XmlDsigGost3411UrlObsolete;
XmlDsigExcC14NTransform transform = new XmlDsigExcC14NTransform();
reference.AddTransform(transform);
reference.AddTransform(new XmlDsigSmevTransform());
reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());
signedDoc.AddReference(reference);
KeyInfo keyInfo = new KeyInfo();
keyInfo.AddClause(new KeyInfoX509Data(clientCertificate));
signedDoc.KeyInfo = keyInfo;
signedDoc.SignedInfo.CanonicalizationMethod = SignedXml.XmlDsigExcC14NTransformUrl;
signedDoc.SignedInfo.SignatureMethod = CPSignedXml.XmlDsigGost3410UrlObsolete;
signedDoc.SigningKey = clientCertificate.PrivateKey;
signedDoc.ComputeSignature();

const string nsSoap = "http://schemas.xmlsoap.org/soap/envelope/";
const string nsSmev = "urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1";
XmlNamespaceManager namespaceManager = new XmlNamespaceManager(document.NameTable);
namespaceManager.AddNamespace("soap", nsSoap);
namespaceManager.AddNamespace("smev", nsSmev);
document.SelectSingleNode("/soap:Envelope/soap:Body/smev:SendRequestRequest/smev:CallerInformationSystemSignature", namespaceManager).AppendChild(document.ImportNode(signedDoc.GetXml(), true));

<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1"><S:Body><ns2:SendRequestRequest xmlns:ns3="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/faults/1.1" xmlns:ns2="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1" xmlns="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/basic/1.1"><ns:SenderProvidedRequestData Id="signed" xmlns="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1" xmlns:ns="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1" xmlns:ns2="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/basic/1.1"><ns:MessageID>db0486d0-3c08-11e5-95e2-d4c9eff07b77</ns:MessageID><ns2:MessagePrimaryContent><ns1:BreachRequest xmlns:ns1="urn://x-artefacts-gibdd-gov-ru/breach/root/1.0" xmlns:ns2="urn://x-artefacts-gibdd-gov-ru/breach/commons/1.0" xmlns:ns3="urn://x-artefacts-smev-gov-ru/supplementary/commons/1.0.1" Id="PERSONAL_SIGNATURE"><ns1:RequestedInformation><ns2:RegPointNum>Т785ЕС57</ns2:RegPointNum></ns1:RequestedInformation><ns1:Governance><ns2:Name>ГИБДД РФ</ns2:Name><ns2:Code>GIBDD</ns2:Code><ns2:OfficialPerson><ns3:FamilyName>Загурский</ns3:FamilyName><ns3:FirstName>Андрей</ns3:FirstName><ns3:Patronymic>Петрович</ns3:Patronymic></ns2:OfficialPerson></ns1:Governance></ns1:BreachRequest></ns2:MessagePrimaryContent><ns:TestMessage /></ns:SenderProvidedRequestData><ns2:CallerInformationSystemSignature><Signature xmlns="http://www.w3.org/2000/09/xmldsig#"><SignedInfo><CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#gostr34102001-gostr3411" /><Reference URI="#signed"><Transforms><Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><Transform Algorithm="urn://smev-gov-ru/xmldsig/transform" /><Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" /></Transforms><DigestMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#gostr3411" /><DigestValue>HBccaGRf0BvRL6sxZnIlNPTlTuPNB8msmQOjt2K46fY=</DigestValue></Reference></SignedInfo><SignatureValue>3yqjcs82E1EsVNxMlsNV+QbNVOEx6DkJ2jQL/BnnP7GXw3Ta2LbnnaB+gtH1cv1yep7OJ5mL2iwfzMuZrIlCZw==</SignatureValue><KeyInfo><X509Data><X509Certificate>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</X509Certificate></X509Data></KeyInfo></Signature></ns2:CallerInformationSystemSignature></ns2:SendRequestRequest></S:Body></S:Envelope>

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring>ЭП-ОВ не соответствует подписанным данным: Ошибка проверки ЭП: Нарушена целостность ЭП.</faultstring><detail><ns3:SignatureVerificationFault xmlns:ns3="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/faults/1.1" xmlns:ns2="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/1.1" xmlns="urn://x-artefacts-smev-gov-ru/services/message-exchange/types/basic/1.1"><Code>tsmev3:PRODUCTION_AREA:TSMEV3_CORE2 : TR:SYNC:SPS:2</Code><Description>SMEV-100:ЭП-ОВ не соответствует подписанным данным: Ошибка проверки ЭП: Нарушена целостность ЭП.</Description><ns3:SignatureVerificationFault>SignatureIsInvalid</ns3:SignatureVerificationFault></ns3:SignatureVerificationFault></detail></soap:Fault></soap:Body></soap:Envelope>