Mexico Digital Signature.
PKI for all Mexico Taxpayers.
The image show a very high level architecture of the PKI that my team and me develop for Tax service in Mexico, the taxpayer send his csr or take it to an office where it will be sent to the Registration Authority who register the public key and sent to key validation to ensure the key is unique between all the universe of keys generated. After the validation, the csr is sent to the Certification Authority who sign the csr and send the X509 Certificate to the taxpayer. All mexican taxpayers can send his tax declaration digitally signed to the authorities and this process improves Mexico tax collection.
In this particular project I have developed the Certification Authority and many parts of Registration Authority along with cryptographic libraries to perform that kind of operations.