New answers tagged

0

The primary key is not able to decrypt information encrypted for a subkey. If you encrypted your backup for a subkey and lose access to the private subkey, you cannot decrypt your backup any more. Things are different with signing. If you lose a private signing subkey, you revoke it and generate a new one. You will never have to use the old signing subkey ...


2

It's really broad to ask about whether a document is considered "secure". Something that is "secure" enough for me, sending a love poem to my girlfriend, is not "secure" enough for Obama, sending a love poem to Putin. As Alexander O'Mara mentioned in a comment, there are different ways of setting a password on a file. Excel gives you several ways to ...


2

Possibly, sometimes. What's exchanged in the initial handshake is not just a symmetric key, but rather a "master key" for the session from which the client and server implementations of the selected cipher suite can extract keys for various purposes. A cipher suite is split into a number of algorithms for different functionality: Key exhange Bulk ...


1

Given the thin details in the story it's hard to be sure, but the simplest explanation is the credentials were not encrypted when the hacker made a copy. The passwords might have been encrypted in a database, but many so-called 'transparent' database encryption schemes serve only to protect the database file from being copied and reused; they ...


1

Passwords should not be encrypted, they should be hashed. Encryption can be easily reversed if you have the key - and an attacker who has managed to steal the whole database probably has stolen the key as well. A hash can not be easily reversed. When someone attempts to login, the server does not decrypt the stored password. Instead it hashes the provided ...


1

The client or the server may request a renegotiation at any time. That renegotiation would include a new shared secret. The Server can send a Hello Request to trigger renegotiation (emphasis mine): The HelloRequest message MAY be sent by the server at any time. Meaning of this message: HelloRequest is a simple notification that the client ...


3

The IV has the same security requirements as the encrypted blocks. For CBC to work, you need to XOR the unencrypted data in the current block with the encrypted data from the previous block. Because there is no block before the first block (so no encrypted block can be obtained) an IV is used instead.


2

I know that many giant companies has spent billions of dollars on how to prevent the privacy of their products but still they cant prevent it... So I am not expecting that I can get 100% solution on this, but still I want to protect it as much as I can. You've already got your answer, you just don't realize it. "As much as you can" is "not at all." ...


0

Windows Embedded with the UI disabled would be a first step. Then you could: Disable the network Epoxy all open ports Remove the floppy drive (do these still exist) As all have said already, 100% is impossible, but if you look at each possible entry point and close it you can get close. Instead of the epoxy method you can setup a USB whitelist to ...


5

All modern encryption methods (AES, blowfish etc.) are designed to be much more secure than you seem to expect. Let us quickly look at some attacks which such ciphers are designed to be resistant against. Known plain text attack - In this case we assume the attacker has access to many plain text blocks along with corresponding cipher text blocks encrypted ...


4

You cannot open a remote file with GPG through FTP. Instead you would need to download the file to the local system and open it there. Because of this the decryption will be done only locally (and will be independent from that way the file arrived on the local system) and thus password for the file will thus stay local too.


7

As mentioned, its impossible to prevent capture of the displayed video - even in the worst case, the user can record the video on a smartphone or using a fixed camera (as some pirate movies do when they are recorded at the cinema) What you can do then is to shift the protection from stopping copying, to prosecuting copiers. You can embed watermarks in the ...


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I think it's easier to split this into its component parts, and consider them as separate entities: AES and CBC. AES itself does not "basically consist of XORing together chunks of the block" - it's a much more complicated affair. Ignoring the internals of it for a moment, AES is considered secure in that without knowing the key, it's practically impossible ...


13

Do not roll your own DRM scheme. The industry have tried and failed so many times that a homebrew solution will stand little chance. It would be better to "stand on the shoulders of giants" and use existing DRM solutions. Windows Media Rights Management and PlayReady are good solutions. The latter supports HDCP and are used by mainstream premium content ...


4

This is a problem of trying to protect what you want to provide. It's impossible to do, but you can make it difficult. Probably the best approach would be to encrypt the files. But at the end, you give all the data for a person to run on a computer they have full access to. Since it will play the video at some times, it means the keys will be available in ...


0

Between a single client and server, the "shared secret" (mastersecret) will have last for the session. Session Resumption may be allowed via Session IDs as described in RFC5247 and RFC4346 or Transport Layer Security (TLS) Session Resumption without Server-Side State is described in RFC 5077 allows The ticket lifetime may be longer than the 24-hour lifetime ...


15

As you state in the question, doing this in a foolproof way is technically impossible. For the video to be displayed on the screen it must somehow reside somewhere in the RAM on the computer, be transfered to the monitor and then displayed there. From all these points the video could be extracted. Possible ways include: Copied from RAM. Recorded with ...


-4

The Initialization vector used is a random number also called nonce which when combined with a secret key makes the original data completely unreadable. The data when first XOR with plaintext data, it randomizes it. Additional secret key encryption will make it even more harder to read. Hence IV essentially need not be secret since the encryption with a ...


8

No, because the key is secret. The "block cipher encryption" block in the diagram scrambles the data depending on the key. The XOR in the diagram does not provide the security, the encryption does. The XOR and the IV are just to make sure the same plaintext encrypts as different ciphertext for each block.


1

Let me answer this based on how PGP/GPG works. So you have a file for say Client X, and you are using FTP as a delivery mechanism. You want to ensure that your data is protected (encrypted) and only Client X can read it. To do so, you would be using your PGP key for signing, and they will use their key for decrypting. You (PGP key which can be looked up on ...


1

It is possible, if your server accepts files uploaded by an anonymous user and if you don't provide a hash (e.g. SHA-256, SHA-512,...) in order to check that cred.gpg actually contains passwords.pdf and not evilfile.pdf.


2

Risks of Exposing Encrypted Information With it being encrypted I assume having it publicly accessed wouldn't affect security as the encryption setup would make it pointless for anyone to try and decrypt it. Your encrypted information will stay private as long as the crypto works (no flaws in the underlying mathematical principles are found), the ...


2

In short: Intercept encrypted communication: yes (attacker gains some metadata) Decrypt content of intercepted encrypted communication: no (presumably) Intercept not-yet-encrypted or already-decrypted communication at either end: yes (attacker would have to alter the client, but government agencies can force WhatsApp/Facebook or Google or Apple to push ...


16

It's very unlikely that any government agency would crack the encryption. They would need the key. And the only way they could get that is if Whatsapp had a backdoor or weakness in their software which allowed for such a key to be extracted. There is, as of today, no direct evidence that such a backdoor exists in Whatsapp. But, since Whatsapp is closed ...


-1

They can intercept it but they cannot decrypt it. Well... So we like to think... there were slides leaked by Snowden that showcased NSA capability for partial decryption of OTR chats over Google Talk.


5

You have asked one question, but I think that you are asking two: can Whatsapp encrypted communications be captured, and can Whatsapp encrypted communications be captured in "the clear" To your first question, all communications can be captured by legal authorities. It's actually not that difficult, and there are multiple examples of this happening. To ...


1

I Have a few suggestions but no definitive best go to solution since it really depends on your specific use case. First off look into BerryBoot, it offers full disk encryption out of the box. A second alternative is to use any of the TrueCrypt like applications such as VeraCrypt It offers a bunch of options to either perform full disk encryption or make ...


5

The answers to the linked question give a very good overview of why quantum computers break modern encryption schemes (RSA and Elliptic Curve Cryptography (ECC)), but not how to mitigate against it. Summary: expect it to take until ~ 2020 to work the kinks out of post-quantum algorithms - Use AES-256 for now! As mentioned in Thomas Pornin's answer to the ...


-1

The only disadvantage of Public key encryption is a key distribution problem: if you need to verify/check your file by multiple software instances, i.e. you're signing an upgrade patch, it's a problem to pass your key untampered to the clients, so forging/MitM will be impossible. If you're about to just encrypt a file - I'd recommend you to use a symmetric ...


8

Your friend is correct in that private key encryption is not the tool for the job. This answer on Cryptography.SE does a good job of explaining why. Some highlights: Any public-key encryption schemes is bound to increase the size of the data that it enciphers. While there are more efficient schemes, it is safe to say that a symmetric scheme is ...


7

Asymmetric cryptography has two common use cases: Encryption: You process a message or file with the public key of somebody else. Only he/she can decrypt it with his/her private key. Signature: You process a message or file with your own private key. The message or file itself can be transmitted unencrypted. It is common to process/sign only a hash of the ...


5

This is a question about scope and application interaction. So where one is better than the other depends on the scope of access of the data. With application layer encrypt the data is only view able in your applications memory space. If this is what you need then application level encryption is the way to go. However when sent to another application, that ...


0

DiskCryptor will likely not benefit from the hardware FDE stuff on the SSD. The best information I can find is that the drive always encrypts, it's just a question of whether or not the key is password protected, as it should be to actually be relevant. If your BIOS/EFI supports it, you can actually enable it there: Security > Password on boot > HDD ...


0

Here is a list of tools I evaluated for us. sysPass sysPass is a PHP web based Password Manager for business and personal use. AES-256 encryption in CBC mode RSA for sending passwords from forms Two factor authentication HTML5 and Ajax interface Users, groups and profiles management (up to 20 access levels) MySQL, OpenLDAP and Active Directory ...


2

Universally Unique ID v 4 with device pre registration sounds about right for this sort of application. When a device is in the factory you flash it's firmware with a UUID in it. Then you register that UUID with the DB. If the UUID exists, you generate and flash a new one. This should be exactly what you want because now if someone grabs a device, they have ...


3

In regards to Boxcryptor, every user has its own RSA key pair which is generated locally on his device and the private key is encrypted with a so-called password key. The password key is derived using PBKDF2-SHA512 from the user's password. The encrypted private key and the public key are stored on Boxcryptor's servers for Boxcryptor accounts or in a local ...


1

The way I would implement it is probably similar to the way many storage providers with encryption capability do. A random key symmetric is generated and used to encrypt the data. 2 copies of the symmetric key are then encrypted, one with a user asymmetric public key, and one with the master asymmetric public key. Only the private keys can then decrypt the ...


1

Most phones have the cellular network interface share some memory with the main processor (I wonder if it's cooperation between manufacturers and carriers/law enforcement to give them potential access to the phones?). As a result, a compromised/malicious cellular NIC could take over the entire machine. There are ways to mitigate this without completely ...


0

I may be sound paranoid and disappointing, but IF your customers are on stock firmwares/spywares/crapwares or - even worse - on iOS, then you have no other option than an external message decryptor/signer, an offline one based on sealed system with pre-seeded key, or - at least - an OTP time-based token. PGP, RSA, SSL, e.t.c. are good unless compromised by ...


1

Long story short: For legacy reasons there isn't away to encrypt SMS as a whole. But what about the message itself? Now I'm not saying you should do this, but you could easily use a key to encrypt the message you want to send, then send the encoded message in a few texts with meta information to link them together. Then you just need another way to send the ...


1

The green folders are encrypted, the locked folders are locked to the user only(possibly password protected, but not encrypted). A quick google search for folder with lock icons windows 10 shows that they can only be accessed by you, and not anyone else. Green on the other hand means actually encrypted. A simple test: Send the peglocked folder to someone ...


2

There is no secure data transmission over SMS. The data is exposed to a large variety of information disclosure threats from and through the telco, from tools which sync your SMS to email (such as Exchange and Google Voice). As Lukas says, it is super-hard to encrypt your data and then send it via SMS. If you're going to build an app, then why use SMS as ...


1

I'm not aware of any existing technologies that do this. It seems to me that any kind of PKI would involve sending data through untrusted carriers and seems generally fraught with peril. In addition, the key lengths you would want to use for your public key may not even fit within a single SMS due to the length and different possible character encoding ...


2

How do I know when a rekey has happened? Should I check any logs, or any specific output? Running sshd in debug more (-d) does not show me anything related to rekeying. It is printed only in debug mode, because it should not be a think you should care about. It should work out of the box as it is. But anyway, you can increase log level from your client ...


3

According to this stackexchange Question Does RekeyLimit property in sshd_config enforce re-keying / key re-exchange? you need to make debug more talkative (-ddd). The debug mode (even with a single -d) is sufficient. All you need to do is trigger the rekeying process. When using OpenSSH as client, simply enter ~R (capital R!) and rekeying will take place. ...


2

Typically if encryption is used, it's proper encryption and the fault is in the implementation. Or if the implementation of the cryptosystem is perfect, there could still be a thousand other things wrong. I'm not sure you're asking the right question when asking whether AES is secure. If you want to judge whether they know what they are doing, you could ask ...


2

If you are learning the basis of RSA cryptography, you will see that you can do it by hand. The principle revolves around simple modular arithmetic. What makes the scheme secure is the used of very large prime number and the difficulty to factor the public key into the two initial primes. The same idea stands for elliptic curves with another hard to solve ...


0

One thing you should consider is whether this value is used in JOIN or GROUP BY clauses in the applications that use this data. For example, if your applications need to assemble a credit history based on the SSN, you would want that value to have been deterministically encrypted in all of your database tables. The alternative would be decrypting every ...


3

James Ellis at GCHQ came up with a pen-and-pencil example of public key cryptography, something he called "non-private encryption." He intended it as an illustration of a public key system. The gist of his system is something like this: You start by creating a lot of short riddles, each having a unique solution, which could for practical purposes be ...


0

Interesting! I got your points although I believe paper and pencil can make unlimited computation. Let's say we have very limited computing power. You and your friends want to do some cryptography in daily life. To obtain a Public-key cryptography, you will need a trusted third party which can authenticate your identity and then generate a key pair ...



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