I am new to Cryptogrphy, HTTPS and SSL !!!
If i am not wrong , the private key of an End Entity certificate (certificate issued by trusted CA like Verisign) is used to decrypt the information sent by the client !
But does a root certificate also have a Private Key?
If Yes, then I wanted to know where exactly the private key of a root certificate is used?
What happens if it is leaked ?
If I am not wrong, the private key of an End Entity certificate (certificate issued by trusted CA like Verisign) is used to decrypt the information sent by the client
You are wrong. It isn't. The peer's own private key is used to sign the certificate so the client can verify that the peer owns the certificate he presents, and the private key of signing certificates is used to, err, sign certificates.
The root certificate's private key is (normally) only used to sign the intermediate certificates. Compromising it allows you to create new intermediate certificates, and by extension, certificates for any domain.
A root certificate is the top-most certificate of the tree, the private key of which is used to "sign" other certificates. All certificates immediately below the root certificate inherit the trustworthiness of the root certificate - a signature by a root certificate is somewhat analogous to "notarizing" an identity in the physical world. If you knew the private key, you could create new (counterfeit) certificates.
Related
I'm confused on how Self-signed certificate works.
Our application will connect to a server to get some info via SSL or https. This mean we are the client. The server is asking us to provide the Self-signed certificate. I created a RSA Key pair and a self-signed certificate.. What cert or key will provide to them? The public key and the self-signed certificate? and do we expect certificate from them?
What cert or key will provide to them?
Only the self-signed certificate should be provided. The private key should be kept private (hence the name).
... and do we expect certificate from them?
This depends if they also use self-signed certificates at their end or if a publicly trusted CA has issued the certificate. In the first case they need to provide the certificate, in the latter case your client just needs to trust the common publicly trusted CA (i.e. what the browsers do).
We have a XMPP server using SSL certificates (for both the server and the clients).
We use a self-signed CA to sign those certificates. Now we want to stop using that self-signed CA, but we have no idea how to replace those certificates to ones signed by an authority like Digicert or GlobalSign, since we don't know what to buy to do the same we usually do (we usually just create a public key, then a request and we sign it using the self-signed CA, and then voila, we have a certificate ready for the client to use)
Any ideas?
Thanks a lot.
we usually just create a public key, then a request and we sign it using the self-signed CA, and then voila, we have a certificate ready for the client to use)
The process is the same as for a Certificate Authority, with the difference you probably have to pay for the certificate
generate a key pair,private and public. (Not only the public)
Generate a Certificate Signing Request including the public key, some data about the certificate as Common Name, and sign it with the private key.
Send the CSR to the Certificate Authority
The CA validates the CSR, builds the certificate and signs it with its private key
Finally the CA sends you the certificate
I have done some research on this but still have some trouble connecting the dots as to what exactly happens when the server send its certificate to the client in terms of verifying signature and root certificates.
When you create a CSR, it generates a private key along with it, and you send it to the CA to generate the cert and sign it, but doesn't the CA use it's own private key to sign? So what is the point of the private key you generated with your CSR?
When server sends its certificate for client to validate, how exactly does client validate that it is a valid CA cert. It has a collection of trusted CA certs, ok - but how exactly are they used to verify that it was a valid CA that signed the server's certificate using the signature and public key of the server certificate? What things are compared to make sure it was not forged?
Is there any point in encrypting your internal self signed certs? How about an internal root cert? Or is the private key the only one worth encrypting?
If we don't keep a database of encrypted data for our web service (over SSL) for example, would we ever care about storing our own private key once we generated the self signed cert, and if we do, they why?
When you create a CSR, it generates a private key along with it
Or you have already generated your own private key.
and you send it to the CA to generate the cert and sign it
You send the CSR. You don't send your private key. It's private. You don't send it to anyone.
but doesn't the CA use it's own private key to sign?
Yes.
So what is the point of the private key you generated with your CSR?
It pairs with the public key contained in the certificate and it is part of the process used to prove that you and only you own that certificate, as only you can generate digital signatures with that private key that can be verified by the public key in the certificate.
When server sends its certificate for client to validate, how exactly does client validate that it is a valid CA cert. It has a collection of trusted CA certs, ok - but how exactly are they used to verify that it was a valid CA that signed the server's certificate using the signature and public key of the server certificate? What things are compared to make sure it was not forged?
The certificate itself is verified, by verifying its digital signature; it is checked for being within its validity period; and then an attempt is made to form a certificate chain using the alleged signer of the certificate (the 'issuer') and the trusted certificates in the collection.
Is there any point in encrypting your internal self signed certs?
No. They are public documents. Only the private key is private, and that isn't in the certificate.
How about an internal root cert?
No.
Or is the private key the only one worth encrypting?
Yes.
If we don't keep a database of encrypted data for our web service (over SSL) for example, would we ever care about storing our own private key once we generated the self signed cert, and if we do, they why?
Because it's private. It is a critical part of your identity. If you leak it, others can impersonate you.
Can anybody clarify to me what kind of "Private Key" is located in a PFX file ?
I am asking this because after having read quite a lot on digital certification I am still a bit confuse on the Private Key part, especially when Certificate Authority is involved.
The part I am missing is where it is said that the Private Key is kept secret on the CA side but if I go in my Personal Certificate Store and I try to export a certificate, I am able to export it with the private key in it.
Is this private key is the same as THE private key that we are not supposed to know ?
Public key cryptography is used for two different purposes when it comes to X.509 certificates used for SSL/TLS.
Each X.509 certificate contains a public key, which has a matching private key held only by the identity this certificate belongs to (the subject of the certificate).
One of the purposes is to build trust in another certificate. A CA uses its private key to sign other certificates: possibly other (intermediate) CA certificates or End-Entity Certificates (the ones that are actually going to be used for the SSL/TLS connection itself).
For example, the Root CA's private key can be used to sign (i.e. issue) an Intermediate CA's certificate. The Intermediate CA certificate can be verified using the Root CA certificate's public key. The Intermediate CA's own key-pair isn't involved in this verification (although the verification process ensures that the public key in that cert belongs to the Intermediate CA).
The Intermediate CA's private key can be used to sign your server certificate (an EEC). The Intermediate CA's public key can be used to verify the authenticity of your server certificate. Someone who would only have the Root CA certificate can therefore check your server certificate by building a chain. Again, your server public and private keys are not involved in this verification at all, but the result of these operations proves that the public key in your server certificate belongs to your server name.
There is no relationship between any of the key pairs involved in a certification chain. Even the CA issuing a certificate will not (or should not) have access to the private key of the certificate it is issuing.
The second usage of public key cryptography is during the SSL/TLS handshake. The exact mechanism depends on the cipher suite, but this allows the client to agree with the server on a secret that only the server with the private key matching the public key in the server certificate will be able to see. It's this private key that is the private key of the certificate itself.
In a PKCS#12 file, you will find an End-Entity Certificate and the private key matching the public key in that certificate, to be used by the entity to which this certificate was issued, and generally a chain of CA certificates (from the one directly issuing the EEC to other CA certificate further up the chain, possibly up to a Root CA).
Here, I've taken this example of an EEC for an SSL/TLS server, but the same could apply for EEC to be used in other contexts (e.g SSL/TLS client or S/MIME).
If you are talking about SSL-Certificates and SSL I think you mean X509-Certificates in common. Let me make it clear first: the passwords of the private keys are different.
The magic here is Chaining of the Certificates, i.e.
Root Certificate from CA
Intermediate Certificate from CA (for instance Class 2)
Your Certificate
If you look at your SSL-Certificate, you will find this structure. Every certificate within this hierarchy can be seen as a certificate for its own. You can find more information within this msdn article. A briefly description from my point of view:
The Certifcates within this chain can be seen are separate Certificates. With their own ability to sign Information with the private key and validating signature with their private key. They are basically linked within this chain.
You might ask Why are the Certificates linked?
There are two main reasons: Security and Trust.
If you loose your private key or if your certificates is broken, it's need to be revocated. This basically says, that your Certificates should not be trusted anymore. It's listed on the Revocation-List on the parent Certificate to ensure that this security break can be fixed very fast. This behavior explains, why root certficates creating IntermediateCertificates and not your requested Certificate - they want to be sure that they can revocate their Intermediate Certificate as well.
Additionally to this functional explanation there is a mathematical, but I am not able to explain this is an easy way. You can find Information about this within it's article on Wikipedia. Basically it says, that you can't calculate the password from the parent and / or public certificate to use the private certificate.
As I understand, the root of SSL security is based on the public key of certificate authority. And I don't know why this key can be faked by a man in the middle:
The man in the middle received this CA public key but then sends me a public key and fake certificate of his own and pretends that it is valid. I use this key to compute the certificate signature to verify it but if this key is fake, how can I know certificate is not from a trusted source?
In order for any PKI to work, each party should have a list of public keys for CA they trust. These keys have been obtained out of band, securely, from a software vendor.
The SSL certificate (containing the SSL server's public key) received from the server is signed by the private key of one of AC. There is no way to forge a valid certificate without access to one of the CA's private key, so the man in the middle can not send a forged one that will look valid.
The is two things that we need trust in order to use PKI :
1/ that we can securely retrieve the CA's public keys
2/ that the CA won't mess up by signing forged certificates or by getting their keys stolen.