109

You can't, plain and simple. If you don't trust the hosting company, you don't host with them. This is law #3 from 10 immutable law of security: Law #3: If a bad guy has unrestricted physical access to your computer, it's not your computer anymore. The hypervisor always have privileged position over your virtualised machine, you can't protect yourself ...


77

As Steffen already said, the Achilles' heel on your security is making sure you are talking to Joe, and Joe being sure he is talking to you. If the initial key exchange is compromised, the third party will be able to read your messages, reencrypt and send to Joe, and vice versa. The crypto does not matter unless you solve this issue. That's why on the HTTPS ...


73

If decryption only relies on the keyfile and this keyfile is readily available, there is indeed no significant security benefit in your setup. What you can do though is store the keyfile on a removable device (e.g. a USB stick) and detach it when you are not around. That way decryption is only possible when you are present and the removable device is ...


73

See the note in the bottom center of this classic slide: This is from a leaked NSA slide deck. Tapping internal traffic is not rocket science, the only real requirement is that someone is targeting you. If there is something of value going over the cable, something potentially worth encrypting, then you may also assume that someone might be going after it ...


63

Sparks stores your account credentials on their systems. This is also described in their privacy policy: INFORMATION WE COLLECT AND HOW WE USE THIS INFORMATION Auth login or mail server credentials: Spark requires your credentials to log into your mail system in order to receive, search, compose and send email messages and other ...


62

There is no way to do this - this is a subset of what DRM schemes attempt to do. If an end user can decrypt something once to see it, they can see it again. Any of the following may be possible: first take a copy and decrypt that copy the screen edit the application The only way you could get close would be to have total control over the hardware and ...


51

The strongest possible way to encrypt data is to start with a threat model. What sort of adversary are you trying to protect your data from? What are they willing to do to get it? All reasonable approaches to cryptography start with one. If you start with one, you stand a chance of finding "the strongest" for your particular situation. I ...


50

tl/dr: Your selected version of the JWT doesn't encrypt anything, it merely encodes it for easy transport. The data in the payload is not meant to be a secret. You have a JWS (JWT with signature). What you are looking at is simply the base64 encoded data payload. A JWS contains 3 parts: The base64 encoded header The base64 encoded data A cryptographic ...


44

The only use case i can think of is if you have untrusted users on the network... This, but the problem is that you have untrusted users who you don't even know are users on the devices on network. This includes: Botnet nodes on compromised IoT junk Developers of whatever sketchy apps you installed on your phone or PC Attackers who've already compromised ...


43

The biggest obstacle to your proposal is user adoption and behavior change. Imagine having to explain to everyone what a public key is and how great it is to have. This is just not going to happen. Instead, email security has moved to the mail server side of things, with multiple goals: transport encryption. This is already fairly widely deployed sender ...


41

This CA Root certificate skole.hr is not an official Eduroam certificate, but a CA certificate probably from the school that implements Eduroam WiFi. It's also plausible that this is a completely unrelated 3rd party CA certificate used for spying; we can't distinguish that with certainty. While it might be used for WiFi authentication, as the ...


38

A cold boot attack is impossible on an offline device. The only way an attacker could use a cold boot attack on your portable storage device is if they also had physical access to your computer as it was plugged in the disk unlocked. A cold boot attack relies on encryption keys being stored in RAM, and the persistence of that RAM once the computer is hard ...


38

For practical purposes, no. Against good crypto, using modern ciphers and making no major mistakes such as a padding oracle or ECB mode or other weakness, it doesn't really help. It can theoretically act as a test for whether you brute-forced the key correctly - does the decrypted file contain the right magic number and data format? Good, you got the right ...


32

If you want the strongest, I’d suggest a one-time pad to encrypt the file. If you want realistic, I suggest you rather expand on what your threat model is and take advice as to the actual level of encryption that you need is.


31

I don't completely agree with the accepted answer for 2 reasons. First, Android provides two distinct import options for a reason.VPN and Apps is for general HTTPS traffic from all of your apps, including browsers. You can install your own CAs here if you want to intercept your own traffic, for example. WiFi is for identifying enterprise WiFi networks, but ...


27

There's a bit of confusion of terminology here. JWT defines the basic format of the claims, and some standard claims. It specifies that the JWT Claims Set should either be the payload of a JWS or a JWE structure. JWS defines a structure for some payload with a signature. While the payload is almost always JWT in practice, this is not a requirement of the ...


25

As you already hinted at, such a thing is only possible in hardware. A software or encrypted data solution would always suffer from the option of making a copy before decryption. In hardware, the scheme would be to destroy information on decryption. A naive approach would be to simply read a block into memory, destroy it on storage and then decrypt it. ...


21

If they decide to manipulate my initial e-mail message, changing the key I sent to Joe, then Joe's reply will be unreadable by me, since it's no longer encrypted using my public key, but Google's intercepted key. That means Joe and I won't be having any conversation beyond that initial e-mail ... As long as you can be sure that they can only man-in-the-...


21

It may seem simple, but it's not. It's actually very complicated. There are a couple moving parts that are difficult to fix: user education: don't count on people knowing what a keypair is, how to create one, how to protect their keys. forgotten/lost keys: if a TLS Certificate is lost, the owner just requests another one. No traffic is lost. But if a user ...


21

To put it simply: There is NO way As you already determined, a request can easily be forged. Even if using a custom encryption, your users can decompile your code and find out how it's done. The only way to prevent users from tampering and decompiling your code is by not handing it to them. Often this is done by providing SaaS products that run server ...


19

so that it would not be economically viable to spend time & resources to get them. I hate to break it to you, but you simply aren't that important. No-one knows you or your web app. So it's already not economically viable. Consider the cost-benefit. For the hosting company, if this happens once, they'd hemorrhage customers. So they're going to have ...


17

There are several possible attacks on Bitlocker, and apparently a software is available to the police that supports recovery of the password (but requires sniffing the RAM while the device is mounted and unencrypted). The primary weakness is the recovery key stored in both AD and the TPM chip - but if your attacker has only the USB stick, those don't apply. ...


17

If you only need to verify the email when the user provides it, then hash it, like vidarlo suggests, in the same way you would hash a password. No need for encryption here. The flip side with this approach is that you can never recover the email, even if you really need it (e.g. to contact your users in case of a compromies, as suggested in comments). If ...


16

If you have no master password set, then the login passwords are always available. If you do have a master password set, then opening the Saved Logins dialog will prompt you for the master password. Without the correct master password, the list of logins will be empty and thus there is no password to copy. The bug only occurs in this specific condition: A ...


16

I know nothing about cryptography. How do we encrypt a file in strongest (emphasis added) possible way such that we can access them some years later. I prefer that it should be fairly resistant from brute force and other possible ways attacks. I need some direction only. Use AES-256 in GCM mode.


14

What you're missing is that your token is signed (or, more precisely, authenticated with a symmetric key) but not encrypted. If you take the token in your question above, split it into three pieces at the periods (.) and feed each piece into a base64 decoder, you'll get the following decoded outputs: {"alg":"HS256","typ":"JWT"} {"sub":"1234567890","name":"...


13

is "Installed for Wi-Fi" which I assume means that the credential is applied to all WiFi traffic. No. It doesn't mean this. There are several ways in which a WiFi network may authenticate a user. The most common ones are: WPA-PSK Both parties use a Pre-Shared Key to authenticate themselves. That is the mechanism for all those that use just a password. ...


13

It's been touched on in other answers and comments, but I think the fundamental difference between web and e-mail traffic is who the parties involved are. HTTPS actually does two things: It encrypts the communication so that it can't be read by an attacker. This is achieved using a stateful session negotiated directly between the user's browser and the web ...


12

Any online service that acts on your behalf with other network services will normally need to store the credentials needed for those other services. While there are other ways to implement authenticate between services, such as OAuth2, in practice very few services implement such mechanisms. So when an online application needs to perform on your behalf, it ...


11

In theory, you should be able to use the trusted hardware features of modern CPUs to run your disk encryption, or even your entire VM, inside a tamper-resistant part of the CPU, having all the data on disk and in memory encrypted with keys that are only accessible inside that tamper-resistant trusted enclave. While exposing Intel's SGX trusted computing ...


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