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Post-quantum cryptography

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Re: Post-quantum cryptography

#11

Post by ams6110 »

tedunangst wrote: post #3
beloch wrote: post #2

Q: Why should we care about this? Why not deal with it when quantum computers finally start cracking existing crypto? A: 1. It takes time to implement new methods. Would it be acceptable for there to be a period of months or years during which we can't make credit card transactions, etc.? 2. Coded text of messages encoded using conventional cryptographic methods can be intercepted, archived and then broken at a later…

> As a general rule, don't use conventional encryption methods to transmit information with long-term sensitivity (e.g. medical records, etc.). So what do you suggest I use today , given that I have a medical record here and I need it over there?

Fax machine

Re: Post-quantum cryptography

#12

Post by Hoff »

tedunangst wrote: post #3
beloch wrote: post #2

Q: Why should we care about this? Why not deal with it when quantum computers finally start cracking existing crypto? A: 1. It takes time to implement new methods. Would it be acceptable for there to be a period of months or years during which we can't make credit card transactions, etc.? 2. Coded text of messages encoded using conventional cryptographic methods can be intercepted, archived and then broken at a later…

> As a general rule, don't use conventional encryption methods to transmit information with long-term sensitivity (e.g. medical records, etc.). So what do you suggest I use today , given that I have a medical record here and I need it over there?

Most recent NSA transitional recommendations are for 3072-bit asymmetric, and AES-256 symmetric.

Details: https://www.nsa.gov/ia/programs/suiteb_cryptography/index.sh...

For network transfers, you'll likely also want to select your encryption with PFS:

https://en.wikipedia.org/wiki/Forward_secrecy

Re: Post-quantum cryptography

#14

Post by Spooky23 »

ams6110 wrote: post #11
tedunangst wrote: post #3

Earlier quoted context omitted.

> As a general rule, don't use conventional encryption methods to transmit information with long-term sensitivity (e.g. medical records, etc.). So what do you suggest I use today , given that I have a medical record here and I need it over there?

Fax machine

Several years ago, I was asked to intervene in an argument with a institution handling extremely sensitive information that needed to be transmitted en masse.

The receiving party received the data on physical media in the mail, but refused to access it, as the tool used to encrypt the data wasn't validated to FIPS 140-2 Level 2. (It was a reasonably good commercial product, and had Level 1 validation, and the folks negotiating this had no clue what that meant anyway) Why did that matter? Who the hell knows.

Their counter proposal was that something like 2,000 pages of whatever would be securely transmitted via Fax.

The punchline is that the stuff ended up getting re-shipped in paper form via Fedex Same-Day, securely nestled in a big pelican case secured with zip ties and a $30 padlock. Everyone shook their heads, except for the poor secretary facing sending 2,000 pages through a fax machine :)

Re: Post-quantum cryptography

#16

Post by gubberdump »

altcognito wrote: post #5
tedunangst wrote: post #3

Earlier quoted context omitted.

> As a general rule, don't use conventional encryption methods to transmit information with long-term sensitivity (e.g. medical records, etc.). So what do you suggest I use today , given that I have a medical record here and I need it over there?

One time pads sent via some secure service is about all I can come up with. This works provided you know who you are going to talk to and don't suddenly run out of "pad". Sounds like an awful business model. I'm sure some consultancy could sell it though.

One time pads are not secure against "beyond-time" tactics or attacks.

Also, all alphanumeric combinations have been generated.

Re: Post-quantum cryptography

#17

Post by nunyabuizness »

Shameless plug: a few months back, I was going thru a coding bootcamp and for a 2-day sprint (forgive me) I wrote a simple, entirely insecure Lamport-Merkle digital signature algorithm implementation [0] in JavaScript based on the "spec" outlined in the Wiki [1].

It uses nothing but Merkle trees and SHA-256 hashes, lacks documentation and should be used by no one, but the code is pretty simple to follow [2] and I'd appreciate any and all comments/criticisms in terms of implementation, optimizations, usage requirements and API improvements:

[0] https://github.com/sunny-g/Lamport-Merkle.js [1] https://en.wikipedia.org/wiki/Merkle_signature_scheme [2] http://blog.sunnyg.io/2014/12/13/merkle-key-trees-and-signat...

Re: Post-quantum cryptography

#18

Post by dogma1138 »

beloch wrote: post #2

Q: Why should we care about this? Why not deal with it when quantum computers finally start cracking existing crypto? A: 1. It takes time to implement new methods. Would it be acceptable for there to be a period of months or years during which we can't make credit card transactions, etc.? 2. Coded text of messages encoded using conventional cryptographic methods can be intercepted, archived and then broken at a later…

Most credit card transactions are atill point of sale which usually uses symmetric encryption so quantum computing doesn't play a role.

Also if tomorrow some one makes a quantum computer which can say break 2048bit RSA easily it won't break the world.

A state actor with a trillion dollar machine won't care about your credit card. And this won't change quickly quantum computing will be very expensive for decades to come.

And moving to symmetric encryption with key exchange instead of classical PKI is always an option.

As a general rule using anything but conventional encryption is a sure way of having your encryption broken unless you are a world grade cryptographer with 50 world grade friends that can audit your system.

Re: Post-quantum cryptography

#19

Post by nickpsecurity »

I originally just told clients worried about this to use a split signature between a top classical one, NTRU, and McEliece. Was always interested in the Merkle Signatures, though, thinking they could be improved. To my delight, there's been quite a bit of progress there including unlimited signatures. I want more peer review before widespread deployment of them, though.

https://www.schneier.com/blog/archives/2015/03/friday_squid_...

My niche, high assurance, has seen a lot of use of old, Merkle trees for memory encryption and obfuscation. A few examples.

https://www.schneier.com/blog/archives/2014/06/friday_squid_...

Note: Merkle seems to be one of the under-appreciated cryptographers of history. His legacy might live on and get better than ever post-Quantum, though. ;)

Personally, I think this is another spot where a mini-Manhattan Project worth of brains should be put into. Specifically, finding more problems that can be turned into good, asymmetric crypto. I'm sure there's already a list of potential ones that a ridiculously hard to solve. Just need bright people thinking hard on how to leverage them for key exchange at the least.

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