Note that this SHA-1 hash itself is not stored with the certificate. It is calculated by executing the contents of the certificate, minus the signature itself, by the SHA-1 algorithm. In this way, any change in the CA is detected immediately – the SHA-1 hash does not match that of the signature. Used when the sender and recipient of the public key need to derive the key without encryption. This key can then be used to encrypt messages between the sender and recipient. Key matching is typically used with Diffie-Hellman ciphers. dataEncipherment does not apply, because what is encrypted is not directly meaningful data, but a value that is usually randomly generated and used to derive symmetric keys. keyAgreement also does not apply because these are key matching algorithms that are not a case of asymmetric encryption (e.B Diffie-Hellman). The keyAgreement usage flag appears in a certificate that contains a DH key, not an RSA key. nonRepudiation is not used because anything signed as part of an SSL/TLS key exchange cannot be used as evidence for third parties (there is nothing in an SSL/TLS tunnel that the client could record and then use to convince a judge to sue the server itself; the data exchanged in the tunnel, are not signed by the server). I need to issue a certificate with this key use: digital signature, key encryption, key agreement (a8) Now it`s interesting – this certificate lists the same entity in the issuer as in the subject. This certificate is called “self-signed”: you can use the public key of the certificate to verify the signature. This is also the same public key used to verify the signature of the previous certificate.
There are no parent certificates – the certificate chain ends here. I`m really concerned about RSA keys, so the exchange methods are RSA (generate a key, encrypt it, and send it) and [EC] DHE_RSA (generate a short-lived DH [EC] key, sign it, and use it for the key agreement). Digital signing, non-repudiation and/or key encryption or key agreement If an RSA key is to be used only for key management, the keyEncipherment bit is also confirmed. Improved key usage IP Security System (126.96.36.199.188.8.131.52.5) Server Authentication (184.108.40.206.220.127.116.11.1) Client Authentication (18.104.22.168.22.214.171.124.2) 126.96.36.199.4.1.311.21.10: Flags = 0, Length = 26 Application Policies Application Certificate Policy: Policy ID = End of Security System IP Application Certificate Policy : Policy ID = Server Authentication Application Certificate Policy: Ide Policy Changer = Client Authentication 188.8.131.52: Flags = 1 (Critical), Length = 4 Digital Key Usage Signature, Key Encryption, Key Agreement (a8) To be used when the public key is used to verify the digital signatures used to provide a rejection service. Indenability prevents the signatory entity from incorrectly denying an action (except for certificate signing or CRL). If a certificate with a protocol is used, use the encrypted key. For example, the S/MIME coating, which consists of encrypting a fast (symmetric) key with the public key of the certificate. SSL also performs key encryption. I only use RSA keys, so the RSA (Generate, Encrypt, and Send a Key) and [EC] exchange methods are DHE_RSA (generate a short-lived DH [EC] key, sign it, and use it for the key agreement). The actual operation in RSA is “key encryption,” and in [EC]DHE_RSA, it`s digital signature, but both are key forms of agreement. So, what “Key Encipherment”, “Digital Signature” and “Key Agreement” are required for each method in the key usage extension? I couldn`t find this anywhere and it probably varies depending on the implementation, so the answer could be one table per implementation. These compatibility settings allow you to select the agreement because encryption is selected by default and blocked for all changes.
Under the signature, I selected the digital signature and under encryption, so that key exchange is only possible with key encryption. (I tried all combinations) Key usage extensions define the purpose of the public key contained in a certificate. You can use it to limit the public key to as few or as many operations as necessary. For example, if you have a key that is only used to sign or verify a signature, enable digital signature and/or inadmissibility extensions. Alternatively, if a key is used only for key management, enable the key monkey. .