Scenario: Assume your PGP key pair is compromised and thus you create a new one. (Or for any other reasons, most common that your key pair is expired.)
Is there any way to re-encrypt the emails with the old key to the new key?
I am using thunderbird/enigmail so a way with these tools would be appreciated, but not necessary. Furthermore I am using gmail, so I would like to have the old emails removed from gmail and replaced with the new encrypted ones. In this context: Is that a good idea at all? Let's assume the attacker has access to the old key and the emails. When I upload the old emails with the new key, is he able to infer anything about my new key?
Assuming the attacker has access to your old key and your emails, you can assume he or she has already decrypted them and has a copy of them locally. Decrypting and then encrypting them won't serve much of a purpose.
If you have a government issued PKI card, you can use MailCrypt (http://iase.disa.mil/pki-pke/Pages/tools.aspx). It is made for situations where your certificates are expiring but you still need access to old encrypted emails. You can re-encrypt with any certificate.
Related
I need to store a sensible info in a database (clients passwords). Is there a common practice? The information should be accessible by various users. Think about service company that should make maintenance of clients systems.
I'm thinking about using AES encryption. All the information is encrypted with the same main key. For every user this main key is encrypted with the user's password used as the key and stored separately. During login and authentication the main key is decrypted and saved in a session. Later the key is used to decrypt clients info. Is it a good practice?
Thanks
P.S.: Yes, I know that it's better not to use passwords, but it's not me to decide the way to access client's servers.
I'm reading about JWT Tokens recently, and I've got a moment; I've got an idea which seems to be great in my head, but I suspect it's not so great when it comes to the end.
I see people are encrypting tokens with single key for global purpose. What if I'd generate completely new key for every user, join two strings afterwards and use the output for encrypting the token? This would deal with need of creating blacklists for users that shouldn't be having access anymore and so on. What I am missing? Because I'm sure somebody had similar idea to mine, and for some reason it's not widely used. Where am I lost?
JWT are signed (not encrypted) with the private key of the issuer, usually the server. A digital signature identifies the signer and protects the content from alterations.
If you modify the payload of a valid JWT, the signature or create a fake token, the server just will reject it. This is why the server does not need a list of issued tokens, because it can verify cryptographically if a token is trusted
You could create a different key for each user, but is not necessary, because you want to proof that the token has issued by the server to trust in the data contained in payload do just one key is needed
I'm implementing a sign in system with the help of the JWT (JSON Web Token) scheme. Basically, after a user sign in / login, the server signs a JWT and passes it to the client.
The client then returns the token with each request and the server verifies the token before sending back a response.
This is pretty much how you would expect it, but I'm having some problems with the logic of the process. From all the mathematical articles I've read, it seems that RSA signing uses asymmetric keys for signing. As the public key, as its name suggests, is exposed to the client and the private key is kept on the server, it makes sense to sign the JWT with the public key which is sent to the client and verify it on the server side using the private key.
However, on every example and library I see it seems to be the other way around. Any idea as to why it is so? If a JWT is signed with the private key and verified with the public one than whats the point?
First off, apologies, this answer got rather long.
If you use RSA to sign your tokens, and a connecting client is a web browser, the client will never see the RSA keys (public or private). This is because the client presumably doesn't need to verify that the JWT is valid, only the server needs to do that. The client just holds onto the JWT and shows it to the server when asked. Then the server checks to make sure its valid when it see's the token.
So why might you need a public / private key combo for JWT's? Well first off, you don't need to use a public / private key algorithm.
You can sign JWT's with a number of different algorithms, RSA being one of them. Other popular choices for signing your JWT's are ECDSA or HMAC algorithms (the JWT standard supports others as well). HMAC, specifically, is not a public / private key scheme. There's just one key, the key, which is used to both sign and validate the tokens. You can think of this as using the private key for both signing and validating the JWT's. I'm not an expert on this by any means, but here's the conclusions I came to from doing my own research recently:
Using HMAC is nice because it's the fastest option. However, in order to validate the JWT's, you need to give someone the one key that does everything, Sharing this key with someone else means that that person could now also sign tokens and pretend like they're you. If you're building multiple server applications that all need to be able to validate your JWT's, you might not want every application to have the ability to sign tokens as well (different programmers might be maintaining the different applications, sharing the signing ability with more people is a security risk, etc). In this case, it's better to have one, tightly controlled private key (and one app that does the signing) and then share the public key around with other people to give them the ability to validate the tokens. Here, the private key is used for signing the tokens, and the public key is used for validating them. In this case you'd want to choose RSA or ECDSA.
As an example, you might have an ecosystem of apps that all connect to
the same database. To log users in, each app sends folks to one,
dedicated, 'logging in' app. This app has the private key. The other
apps can verify that the person is logged in using the public key (but
they can't log people in).
The research I've done points to RSA being the better option for most JWT apps in this scenario. This is because your app will be, theoretically, validating tokens frequently. RSA is much faster then ECDSA at verification. ECDSA is primarily nice because the keys are smaller in size. This makes it better for HTTPS certificates because you need to send the public key to the client's browser. In the JWT scenario though, the keys are staying on a server so the storage size is n/a and the verification speed is more important.
Conclusion: if you're building a small app without multiple smaller 'micro-service apps' / you're the only developer, probably choose HMAC to encrypt your keys. Otherwise, probably choose RSA. Again though, I'm not an expert, just someone who recently googled this topic, so take this with a grain of salt.
There is a difference between signing/verifying and encrypting/decrypting data but the semantics can be similar.
You sign data with a private key that only controlled sources have so anyone who receives the information can use your public key to validate this information was indeed sent by you and is the same information you intended to send out.
You encrypt data with a public key and decrypt with a private key. This sounds opposite but really follows the same logical concept as signing. If you want to send data between person A and person B, both people have a public/private key pair and they share their public keys with each other when they meet (handshake). A constructs a message for B and encrypts it using B's public key and sends it to B. Now, no one without B's private key can decrypt that message including A - even though they originally sent it.
In terms of JWT, a JWT payload by itself is just Base64 encoded JSON with some standardized fields. The signature allows someone with the public key to validate the information hasn't been altered by someone in the middle. Similar to a checksum but with some extra security based warm fuzzy feelings. The contents of the signed JWT are easily visible (base64 is encoding like unicode or utf-8, not encryption) to the end user and anyone in the middle which is why it is generally frowned upon to send sensitive data in a JWT like passwords or PII.
As others have mentioned, most JWTs contain information not intended for clients but to help facilitate the stateless part of RESTful services. Commonly, a JWT will contain an accountid, userid and often permissions as "claims". An API endpoint can verify the signature and reasonably trust the claims to not be altered by the client. Having the client send the JWT for each request saves the endpoint having to do a lot of database back and forth just to get where they are by simply verifying a signature with a public key.
Additionally, signed JWTs can be encrypted. According to the JWE spec, the payload is encrypted after signing and then decrypted before verifying. The trade off here is that all endpoints must also have the private key to decrypt the JWT but end users won't be able to see the contents of the JWT. I say trade off because in general private keys are meant to be kept secure and a widely distributed private key is just less secure. Security, risk assessment and cost/benefit of encryption is a whole other beast :)
Your suggestion:
it make sense to sign the JWT with the public key which is sent to the
client and verify it on the server side using the private key.
is not correct. Signing is done with the private key of the sender, encryption is done with the public key of the receiver. That is how PKI works in general.
I'm developing the set of applications, that provide the possibility to read encrypted data between several users using email messages.
It's rather hard... If to compare email messaging with the live chatting (IMs) through single server (for live chatting, I need just chanell with TLS). because I need to decrypt the the message, which is just saved on remote server.
Also, as I suppose the secure server mustn't keep private keys, because the user wants to be sure, that event supplier side (backend) can't decrypt content. Private keys must store on some stuff like smart-cards (which only user has).
For emails, I've found two options:
S/MIME
OpenPGP
So... the main problem (for me) is how to distribute private data, which will allow to decrypt email message for the user, which received the encrypted email message.
So, question is about correct distribution of private keys, right now I can't imagine how to deliver it in secure way.
Private keys are, well, private. You don't want to be transferring them. Never.
Instead, re-think the problem in terms of distributing the public keys in the other direction. Then you don't need to worry about eavesdropping (but you will want to be concerned with authenticity).
The proper approach is to use asymmetric cryptography to secure the data. In this scenario your users send each other their public key, and they can do this in any way. Private keys remain on user's side. The sender encrypts the data with the public key of the recipient, the recipient uses the private key to decrypt the data.
If you absolutely must use symmetric algorithms and keys for encrypting the data, then you still can use asymmetric cryptography to deliver symmetric keys in encrypted form (this is what S/MIME and OpenPGP would do for you, actually).
Note: when I am talking about encryption with a public key, I mean a hybrid scheme, when the data is encrypted with a symmetric session key, which is then encrypted with a public key. The data are almost never encrypted with asymmetric cryptography directly, without employing a symmetric algorithm.
For iphone push notifications SSL certificates, you need to provide them with CSR files...
I have saved a CSR file since some time now, and i always give upload the same CSR file, whenever i want to generate the SSL certificates...
Now i've been thinking, since when generating CSR files, i'm actually generating the private key, and probably the public key too...
So i'm wondering what disadvantages i'm facing when i'm using the same CSR file.. though when i download the SSL Certificates, they appear in the keychain as if there's multiple private keys (though they have the same name) and each is attached to a different SSL Certificate.
Is it recommended to generate a new CSR file everytime? and why? and if it's not necessary, then how?
thank you
Certificate Request contains the public key and you have an associated private key. So by re-using it you basically get the same key pair signed again and again.
The disadvantage is obvious - if one key gets leaked, you get all certificates compromised. This is why re-generation of key pairs each time is necessary.