With the electronic certificates that are of interest here, a digital signature confirms it is genuine. Getting public keys There are two ways to get access to the issuing office's public keys. The existing chain of certification is followed until a signature with an undoubtedly known key is produced. There are various ways to generate this chain. The alternative is to build a hierarchy with the root certification agent at the top and which all-powerfully knows all signatures because it has all the public keys in its possession.
Hybrids are possible.
The description of the of a certificate's syntax takes place with the help of the ASN.1 specification language . After these entries there is the digital signature. The method used here is called md5withRSAEncryption . The MD5 hash function processes the information into a type of specimen sum and encrypts the result in accordance with the RSA algorithm. Finally comes the actual signature.