How does it work?
The digital signature of a document is the result of applying a determined mathematical algorithm, known as hash function, to its content and, then, applying the signature algorithm (in which a private key is used). This results in the digital or electronic signature.
The digital signature software is also aimed at validating the following:
- Validation date of the digital certificate of signer,
- Revocation of the digital certificate of signer (by OCSP or CRL),
- Inclusion of the time seal.
The Hash Function is a mathematical algorithm that allows calculation of total value of the data when digitally signed.
The hash function only works one way; therefore it is not possible to calculate the original data based on total value.
When the entry is a document, the result of the function is a number that unequivocally identifies the text.
If this number is attached to the text, the sender may reapply the function and prove the result.
However, these types of operations are not meant to be performed by the users, but by a software, that applies the function automatically calculating the hash value and then, verifying it.
