New answers tagged

0

Before the details : Telegram's server side code is not available as open source and hence can't be reviewed. Telegram uses Diffe-Hellman for key exchange and AES-IGE encryption. The basic principle of understanding in DH key exchange is that No entity can effectively intercept the key generation while simultaneously making sure that the parties ...


0

WhatsApp derives the QR code (and the numerical representation) from the user identifier and the 32-byte public Identity Key of both parties. I guess that some deterministic algorithm decides, witch of the two identifiers comes first (e.g. they could be sorted lexically). This allows both clients to display the same image and numerical representation, ...


1

KW allows you to establish a long term secret but still use a different CEK for each message, this is important for some use cases, but not all. In the case of using JWE to send a single message to multiple recipients who all have different long term keys, this is essential as you need to wrap the CEK multiple times once for each recipient. JWE supports a ...


0

This is fairly easy to understand. Simply symmetric encryption use single key for encryption and decryption while asymmetric use different keys (4 different keys). Main disadvantage of symmetric key is the damage, if someone get your key. He can read your messages(sent/receive). Because you use the same “compromised key” for encryption and decryption.(Read ...


1

The main disadvantage of using a shared key in encryption is that you cannot use it to ensure non-repudiation. If you got a message and you are able to decipher it, there is no proof that the sender did encrypt it, because one can still argue you encrypted it yourself.


2

The disadvantage of symmetric encryption Symmetric encryption always use the same key for encryption and decryption - that is the very definition of it. That has one major downside. If the person doing the encryption and the decryption are not the same, they have to somehow securely share the key. If A generates a random key and encrypts a message for B ...


2

A point not previously mentioned: Double encryption. I.e, you first encrypt your message with your favorite secure non-backdoor method, then send the message encrypted again using the government-sanctioned escrow system. This will look no different than using the escrow system to encrypt plaintext, so as far as the government is concerned, you are an ...


4

The answer by Little Code is correct in that it is absolutely not safe to reuse part of the key as an IV, particularly if you intend to use the key to encrypt more than a single piece of data. HOWEVER: That is not what the code snippet you reference in your question is doing. Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(password, salt); ...


5

Is it safe to use a part of the key as IV and what is best practice? In a word. NO. IV is a fundamental part of cryptography that forms part of the essential element of randomisation. The use of a non-cryptographically random IV that is static or otherwise predictable as part of your encryption process means that you are potentially weakening the ...


6

Either you give the public key to Bob when you physically meet him and mutually verify identities (as at a key-signing party), or Bob verifies your public key through a trusted introducer (e.g. a Certification Authority) This is the "Infrastructure" part of PKI.


3

In practice all symmetric encryption algorithms are just algorithms that scramble data with a key, therefore you will always get some output data, even if you decrypt with the wrong key but will most likely just be random nonsense data. The standard method is to hash the message with HMAC to get authentication. Most common is to do HMAC over the encrypted ...


4

Assuming all of the above is feasible, what problems can arise from this system? No one has yet mentioned one of the biggest problem with key escrow systems and backdoored crypto, so I will. User adoption. No one is actually going to use a system that allows an unauthorized 3rd party to decrypt their traffic. It's been tried. The Clipper chip was a ...


6

Some disclaimer-like thingy. Others have made very good points which were partly repetitions of the ones others made before and I don't want to repeat them. So I'm just going to add a little extra which happens to be too long for a comment. Also, I realize that this answer doesn't included a whole lot of technical details. That's simply because the ...


1

I'm not extremely familiar with this topic, but it seems like the "tamper-proof" database could actually hinder this scheme. Once the key arrives, it is stored in an offline, airgapped database that can only be accessed in a single room with rigourous safety. In addition, the database and the machine it is located have tamper protection, similar to ...


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I think that a word combo "Safe Backdoor" needs medical attention ;) There's NO "GOOD NGO" and NO UNCORRUPTED GOVERNMENTS - Ed Snowden proved it in depth and in full. The answer to this question is an old Apple's official statement, that said : "it's technically impossible to create a key that will work only in a hands of good guys and in a rightful ...


15

When a legitimate law enforcement organization has need of a key to decrypt, it sends a formal request to the NGO. The NGO first analyzes the request based on the importance of the request. the NGO allows decryption when the suspect is strongly incriminated by other evidence, and only in the case of terrorism, murder or abuse of a minor (which are ...


3

Assuming all of the above is feasible, what problems can arise from this system? The problems that arise from the system that others have described all lead back to a single thing. The definition of "safe backdoor" has never been given. Both in your question and in the current discussions that are on-going in the United States and other nations, the ...


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In addition to the points mentioned by Lucas Kauffman I would elaborate on point two: 2.This algorithm generates one extra unique decryption key when used. This key is then sent via a secure channel (i.e. HTTPS or equivalent) to an NGO with the sole duty of guarding these keys. As soon as the tool gets confirmation that it is delivered, the tool ...


35

Would an encryption scheme that generates an extra key to be securely stored offsite be a safe backdoor? No. Simply no. A backdoor is never considered safe. What you are describing is commonly known as a key escrow. Note that there have been issues with key escrows: On a national level, this is controversial in many countries due to ...


1

I'm not going to go into the technical aspects - others have already answered that, and it's not really what the question is about. Rather, you can say a couple of things. My answer will be somewhat US centric because that's what I'm familiar with, but similar examples will exist elsewhere. It is also somewhat broader - rather than specifically focusing on ...


3

Take a look at this technical white paper from WhatsApp, they recently moved to the Signal Protocol for e2e encryption. Public Key Types Identity Key Pair – A long-term Curve25519 key pair, generated at install time. Signed Pre Key – A medium-term Curve25519 key pair, generated at install time, signed by the Identity Key, and rotated on a periodic timed ...


2

You can wait until the syndicate finishes their reign of terror and releases the key. For example, all the keys for TeslaDecrypt are now available, so ALL versions can be decrypted now without having to pay. I just recovered some files for a friend who kept his encrypted files from when he was attacked, and can now decrypt them all. ESET Releases Decryptor ...


4

Well if you're really really really serious about the security of your keys then there's only one answer. HSM Encrypt your data at rest using a symmetric algorithm and encrypt the keys used for the symmetric algorithm using asymmetric keys, the private key for which is stored in the HSM. HSMs are carefully and purposefully designed so that once on them, ...


2

Your problem is less about places to put things, and more about whom to trust. No matter what, the password is going to be stored somewhere that someone has access to. You have to trust that person or persons. The most logical choice is to limit access to just the environment where the code runs. That means a limited set of system-admins. These people ...


1

It is a bad idea to generate the key for asymmetric cryptography totally on predictable data (i.e. user chosen password) instead of secure random data. By basing the key completely on predictable data the key gets the same predictability as the password used as input. Still, asymmetric cryptography can be used for authentication/login but not in the way you ...


0

No, there is only one public key in the certificate. Obviously the server should also have the private key that belongs to the public key in the certificate. The session key is retrieved using key establishment. There are basically two ways: the master secret is generated and then encrypted by the client using the public key of the server, the server can ...


2

Q: How to do you decide that a particular key is a weak key? That depends on the cipher (the algorithm itself). According to Wikipedia: In cryptography, a weak key is a key, which, used with a specific cipher, makes the cipher behave in some undesirable way. Q: I got some things like in case of WEP , the weak keys are those whose ...


0

There are different methods and standards, but here are the "common human-readable guidelines" : The algorithm. If it is weak - a 1Mbit long key is a weak key, i.e. it can't protect the data properly The key size. If the algorithm is strong(=it is a way too laborious to brute-force it or repeat it), the key size comes into a play: for example, AES is a ...


-2

Cryptography is the technological equivalent to the Bill of Rights. Just like, say, the right to a fair trial sometimes seems silly when the case is crystal clear, we anyway would not want to do away with it just for the convenience of an exception.


3

There's plenty of good answers here, but I'd like to point out one non-security answer: your friends always say that it's fine to break encryption for "bad guys/criminals/terrorists". But that's not how this is going to be used, even in theory (and law). Whatever the approach, this will apply to anyone suspect of being a "bad guy/criminal/terrorist". And ...


5

Cryptography provides not just security, but also privacy. So the same arguments that apply to debates about privacy vs. safety also apply here. With privacy vs. government surveillance, many may argue, "if you don't have anything to hide, you have nothing to worry about!" ACLU and other organizations have made excellent articles to respond to that ...


3

Ask them if they would be okay with the bank storing their PIN and account number on pieces paper on a billboard in front of the bank. Or their porn viewing habits on front of their house. Cryptography is literally everywhere. Discussing what-ifs doesn't change the fact that cryptography will never go away, it's like trying to have a discussion about the ...


31

My response here is likely many in a sea of answers, but here's the breakdown of why encryption is good, why it's vital, and why breaking it is pointless. - Congress investigation found not a single terrorist plot was stopped by the NSA. So it's all taxpayer's cost for no profit See here. FBI Coleen Rowley at the London's whistleblowers conference ...


-5

[Non-techie friends] clearly would say "no, i do not want the government to have a copy of my house key and watch me doing private stuff. But if they are looking for a terrorist/criminal, it's fine to break the door". It sounds like your non-techie friends are onto something. As most answers have said, this isn't a technical question, it's an ...


7

I am going to take a bit of a different turn to answer the question. It is impossible to prevent the use of encryption, so everyone should use it. If for some reason encryption were to be banned, what would prevent people from using the current algorithms and transmit data? All data is is bytes so you could not even prove that it was encrypted in the ...


3

The primary reason why encryption exists, particularly public encryption, is that many clients must be 'publicly' able to send secret messages or communication,which is not only used by facebook and google, but pretty much the whole internet. Today, we are moving to a world, where everything can be done online,from transferring money overseas(online banking) ...


2

Say I am using SHA-1 which outputs 160 characters string, and my input string is 161 characters, so does that mean each of my 161 character message has at most unlimited collisions and at least 10 collisions/pre-images each of 161 characters. Is my understanding correct? No. First it cannot have unlimited collisions since the number of messages with ...


1

As you already determined correctly multiple images resulting in the same hash must be possible. The argumentation is simple: there is a limited number of hashes and an unlimited number of images which means that there must be multiple images resulting in the same hash.


-1

Here is the comparison between MD5 and SHA1. You can get a clear idea about which one is better.


9

The way I like to explain things to people is through movies. Last night I watched the movie Sneakers. The entire plot of the film is about a "little black box" that can break any encryption anywhere. SPOILER After stealing the box from the University Professor who invented it, it gets into the hands of the bad guys- the head honcho himself explaining ...


58

The thing I haven't yet seen anyone mention is: Ordinary criminals are far more common than terrorists. While crypto might help a terrorist evade the FBI (for a while, anyway) it also helps protect you from ordinary criminals who want to steal your money and hijack your computer for their own ends. The question is, will you concretely give up your safety ...


16

I agree with the "It protects your bank transactions" answer, but I'd like to add a few thoughts: Even if the government banned encryption or forced a backdoor, it wouldn't stop terrorists. Encryption isn't a physical good- it's a mathematical process. Banning encryption would be like banning adding or multiplying (or large semiprime numbers)- criminals ...


0

You could run ent to see how much entropy a file has, a file with high entropy is likely either compressed or encrypted (or both). A problem is that JPEG, XLSX and ZIP are compressed, so actually compressed files are very common. If you suspect that X is an encrypted version of file Z then you could check if they have similar sizes, plus small delta for ...


67

Explain it with questions: Do you close the door when you poop? Why? Everybody poops, you aren't doing anything special in there, so what do you have to hide? If someone leaves a pile of poop downtown in the middle of the road does that mean we must all poop with door open? Simply because the pile of poop was gathered in a bathroom?


0

If you are in hurry. Let me give you my personal opinion. Just understand the following words which I am going to list.. 1.data authenticity 2.data integrity 3.data encryption Common in all security protocols ipsec,SSL,any kind of security. How to provide these all using openssl 1.related words regarding to data authentication and integrity,encryption. ...


0

This book - https://www.feistyduck.com/books/bulletproof-ssl-and-tls/ by Ivan Ristić is best in the market for answering your question. I have read both mentioned books here. But, this book is a gem. It will teach you all the basics with negligible mathematics. It will properly give you recommendation on how to correctly deploy ssl/tls server using openssl. ...


5

Try thinking just as much of how you present as much as what you present I'm going to present my argument with a few attention grabbing words here... but in truth what you need to do is start a discussion much life we do here. A good way is to grab their attention. If a knife is used to kill a man, is that knife evil? Obviously the answer to that is no. ...


16

This is kind of a twisted point to make to anyone who's not familiar with the most trivial details of encryption and security, but I think it stands. Zach still said it best. Encryption is the equivalent of keeping your pants on when you visit the Internet. It should be basic, and it's not our fault that banks and stores are willing to forgo a "no shirt, no ...


45

Imagine if, during the civil rights era, people had access to things like email and smartphones. People like the organizers of the Montgomery bus boycotts would have a little pocket computer that could tell the authorities where they’d been, who they talked to, and what they were talking about. The authorities, at the time, considered these people ...


79

I would take their argument and replace "cryptography" with "locks and keys on our houses" and see if they still agree: If more terrorists and criminals would be caught by not having locks and keys on our houses, I would not blame warrantless searches by government and companies in our homes.



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