procedure TEncodeDecodeFSS(ProvCSP: string; EncryptMessage: string);
begin
    GostSoap := TGostDecryptSOAP.Create(Self);
    try
      GostSoap.Connect;
      try
          mSignature.Lines.Text := GostSoap.decryptMsg(ProvCSP, EncryptMessage);
      finally
        GostSoap.Disconnect;
      end;
    finally
      FreeAndNil(GostSoap);
    end;
end;

    CheckCryptoCall(CryptGetUserKey(ACryptoProvider, AT_KEYEXCHANGE, @hPrivateKey));
//    CheckCryptoCall(CryptAcquireCertificatePrivateKey(rec^.Cert, CRYPT_ACQUIRE_COMPARE_KEY_FLAG, nil, @hPrivateKey, @keySpec, @callerFree));

    // Формирование BLOB-ов публичного и сессионного ключей ФСС на основе зашифрованного ключа из ответа ФСС
    GetResponseKeysBlobs(ASOAPResponse, remotePublicKeyBlob, remoteSessionKeyBlob);

    // Получение ключа согласования импортом открытого ключа ФСС (отправителя)
    // на локальном закрытом ключе (получателя).
    // ошибка происходит здесь
    CheckCryptoCall(CryptImportKey(ACryptoProvider, @remotePublicKeyBlob[0], Length(remotePublicKeyBlob), hPrivateKey, 0, @hAgreeKey));

procedure TfrmSignatureFromCertificate.GetResponseKeysBlobs(
  ASOAPResponse: IXMLDocument; out APublicKeyBlob,
  ASessionKeyBlob: TByteArray);

const OpenPublicKeyBlob: array[0..35] of byte =
      ($06,       // bType = PUBLICKEYBLOB
       $20,       // bVersion = 0x20
       $00, $00,
       $23, $2E, $00, $00, // KeyAlg = ALG_SID_GR3410EL
       $4D, $41, $47, $31, //Magic = GR3410_1_MAGIC
       $00, $02, $00, $00, // BitLen = 512
       // bASN1GostR3410_94_PublicKeyParameters
       $30, $12,
       $06, $07 ,
       $2A, $85, $03, $02, $02, $24, $00,
       $06, $07,
       $2A, $85, $03, $02, $02, $1E, $01);

  trBlob:  array[1..71] of byte =
  ($01, $20, $00, $00, $1E, $66, $00, $00,
   $FD, $51, $4A, $37, $1E, $66, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, // ключ
   $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00,
   $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00,
   $30, $09, $06, $07,
   $2A, $85, $03, $02, $02, $1F, $01); // UKM (157,8)
var
  i: integer;
  transportNode: IXMLNode;
  transport, publicKey, sessionKey,
  sessionSV, sessionMAC: TByteArray;
  trText: string;
  enc: TUTF8Encoding;
begin
  try
    transportNode := ASOAPResponse.DocumentElement
                     .ChildNodes[1]  // Body
                     .ChildNodes[0]  // EncryptedData
                     .ChildNodes[1]  // KeyInfo
                     .ChildNodes[0]  // EncryptedKey
                     .ChildNodes[2]  // CipherData
                     .ChildNodes[0]; // CipherValue

 //изначальный код
{    transport := TNetEncoding.Base64.DecodeStringToBytes(transportNode.Text);}
//мои переделки под Delphi7
    enc := TUTF8Encoding.Create;
    try
      transport := TByteArray(enc.GetBytes(transportNode.Text));
      trText := Q_Base64Decode(enc.GetString(TBytes(transport)));
    finally
      FreeAndNil(enc);
    end;
    SetLength(transport, length(trText));
    system.Move(Windows.PByte(trText)^, Pointer(transport)^, length(trText));

    publicKey := Copy(transport, 93, 64);
    sessionKey := Copy(transport, 7, 32);
    sessionMAC := Copy(transport, 41, 4);
    sessionSV := Copy(transport, 159, 8);

//изначальный код
{    APublicKeyBlob := 
      [
       $06,       // bType = PUBLICKEYBLOB
       $20,       // bVersion = 0x20
       $00, $00,
       $23, $2E, $00, $00, // KeyAlg = ALG_SID_GR3410EL
       $4D, $41, $47, $31, //Magic = GR3410_1_MAGIC
       $00, $02, $00, $00, // BitLen = 512
       // bASN1GostR3410_94_PublicKeyParameters
       $30, $12,
       $06, $07 ,
       $2A, $85, $03, $02, $02, $24, $00,
       $06, $07,
       $2A, $85, $03, $02, $02, $1E, $01
      ] + publicKey;



    // сборка SessionKey BLOB из статической части и параметров сессионного ключа
    ASessionKeyBlob :=
    [
     $01, // bType = SIMPLEBLOB
     $20, // bVersion = 0x20
     $00,$00 ,
     $1E,$66 ,$00 ,$00, // KeyAlg = CALG_G28147
     $FD,$51 ,$4A ,$37, // Magic = G28147_MAGIC
     $1E,$66 ,$00 ,$00] // EncryptKeyAlgId = CALG_G28147
     + sessionSV + sessionKey + sessionMAC +
    [// ASN.1 Sequence + OID Header
       $30 ,$09 ,$06 ,$07,
     // OID_GOST_R28147_89_CryptoPro_A_ParamSet 1.2.643.2.2.31.1
     $2A ,$85 ,$03 ,$02 ,$02 ,$1F ,$01
    ];   }
//мои переделки под Delphi7
    SetLength(APublicKeyBlob, 100);
    for i := 0 to 35 do
      APublicKeyBlob[i] := OpenPublicKeyBlob[i];
    for i := 1 to 64 do
      APublicKeyBlob[i + 35] := publicKey[i];
    setLength(ASessionKeyBlob, 134);
    for i := 1 to 71 do
      ASessionKeyBlob[i] := trBlob[i];
    for i := 1 to 8 do
      ASessionKeyBlob[i+16] := sessionSV[i];
    for i := 1 to 32 do
      ASessionKeyBlob[i+24] := sessionKey[i];
    for i := 1 to 4 do
      ASessionKeyBlob[i+56] := sessionMAC[i];
  finally
    SetLength(sessionSV, 0);
    SetLength(sessionMac, 0);
    SetLength(sessionKey, 0);
    SetLength(publicKey, 0);
    SetLength(transport, 0);
  end;
end;

    GostSoap := TGostDecryptSOAP.Create(Self);
    try
      GostSoap.Connect;
      try
        soapRequestDoc := LoadXMLDocument('FSSEncryptXML.xml');
        try
          decryptMessage := GostSoap.decryptMsg(CP_GR3410_2001_PROV_A, soapRequestDoc.DocumentElement.XML);
        finally
          SoapRequestDoc := nil;
        end;
      finally
        GostSoap.Disconnect;
      end;
    finally
      FreeAndNil(GostSoap);
    end;

  EncSoap := TGostEncryptSOAP.Create(Self);
  try
    EncSoap.Connect;
    try
      EncryptedResponse := EncSoap.encryptMsg(CP_GR3410_2001_PROV_A, CertName, SignedXML);
      mEncryptedResponse.Text := EncryptedResponse;
    finally
      EncSoap.Disconnect;
    end;
  finally
    FreeAndNil(EncSoap);
  end;

  DecSoap := TGostDecryptSOAP.Create(Self);
  try
    DecSoap.Connect;
    try
      DecryptedResponse := DecSoap.decryptMsg(CP_GR3410_2001_PROV_A, EncryptedResponse);
      mDecryptedResponse.Text := DecryptedResponse;
    finally
      DecSoap.Disconnect;
    end;
  finally
    FreeAndNil(DecSoap);
  end;

    CheckCryptoCall(CryptGetUserKey(ACryptoProvider, AT_KEYEXCHANGE, @hPrivateKey));

    // Формирование BLOB-ов публичного и сессионного ключей ФСС на основе зашифрованного ключа из ответа ФСС
    GetResponseKeysBlobs(ASOAPResponse, remotePublicKeyBlob, remoteSessionKeyBlob);

    // Получение ключа согласования импортом открытого ключа ФСС (отправителя)
    // на локальном закрытом ключе (получателя)
    CheckCryptoCall(CryptImportKey(ACryptoProvider, @remotePublicKeyBlob[0], Length(remotePublicKeyBlob), hPrivateKey, 0, @hAgreeKey));

    // Установка параметра PRO_EXPORT алгоритма ключа согласования
    keyParam := CALG_PRO_EXPORT;
    CheckCryptoCall(CryptSetKeyParam(hAgreeKey, KP_ALGID, @keyParam, 0));

    // Получение сессионного ключа импортом сессионного ключа ФСС (отправителя) на ключе согласования
    // Вот здесь и происходит ошибка.
    CheckCryptoCall(CryptImportKey(ACryptoProvider, @remoteSessionKeyBlob[0], Length(remoteSessionKeyBlob), hAgreeKey, 0, @hSessionKey));