How to generate SignatureValue and DigestValue?

Question

Licenses for software and other works

There is a license in which the organization and the term of this license are registered, I tried to replace just the end date, it didn’t work, I think the whole problem is in the SignatureValue and DigestValue lines that check the date. How can I generate these signatures and change the license validity period.

<License>
<Name>"Название организации"</Name>
<Inn>ИНН</Inn>
<Kpp>КПП</Kpp>
<ClientCode>КОД КЛИЕНТА</ClientCode>
<StartDate>Дата начала лицензии</StartDate>
<EndDate>Дата окончания лицензии</EndDate>
<Type>Не знаю что</Type>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
<Reference URI="">
<Transforms>
<Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
<DigestValue>Fl4pPi/Ou8jwjFkaDYj5vn+VqIg=</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>Tr8KmJDyChKhWDVa8xqkoL+PBunC1evBRv/a6rQHuYUrfCK402lXdjRJkcN/FtHGY2Ahqk5zrOFBoHMl7i7TorEEFYNvBss7rbEJ5ofm95mnlbSyBiskGSerSTx9whpmdbq8nn/+lHUde2MqKIQqHCrXzllSc3KCkncPtHNYBNU=</SignatureValue>
</Signature>
</License>