Ask a physicist anything. (3)

[Biologist]

I think it's because the next prime, whatever it is, will push brute force decryption time from a maximum of a matter of days to a length of time that is several orders of magnitude longer than the age of the universe. That seems like way too big a leap, but, who knows.

Brute force decryption already takes much longer than the age of the universe. Serpent and Two-fish methods are for all practical purposes uncrackable.

If a century is a reasonable time frame to recover a key and there are ~10^77 keys in a standard encryption method today. You would have to test 31.709 million trillion trillion trillion trillion trillion keys every second. The current #1 supercomputer in the world does 1.7 * 10^15 flop/s but we will call it 3.1709 * 10^15 for this experiment and we will say it only takes 10 flop/s to test a key. You would need 100,000 trillion trillion trillion trillion super computers of today to crack such a key in a century and it would only cost 10 trillion trillion trillion trillion trillion dollars.

Classical cryptography is not technically uncrackable, it's just so time-consuming for a classical computer to do it may as well be. Quantum computing, on the other hand, will be able to crack it much faster, so I'd say the industry standard will need to shift to quantum cryptography eventually if quantum computers become standard.

Much faster, is still many times the age of the universe.

 

[pgp_protector]

Question.
If you encrypt an encrypted file would that make it even harder to crack ?

 

[Wiccan_Child]

Question.
If you encrypt an encrypted file would that make it even harder to crack ?

That's what I've always wondered. If you double-encrypted it, brute-force methods would be pointless: the algorithm that measures the 'readability' of the cracked text wouldn't be able to distinguish the correctly decrypted text (which still has a layer of garble on it) from the doubley-garbled text. And even if it could, decrypting text twice would still take more time, wouldn't it?

 

[Biologist]

Question.
If you encrypt an encrypted file would that make it even harder to crack ?

Yes and No. Yes because you have to factor two keys instead of one. No because at that point the passphrase is usually the weakest link because with it you have both keys.

That's what I've always wondered. If you double-encrypted it, brute-force methods would be pointless: the algorithm that measures the 'readability' of the cracked text wouldn't be able to distinguish the correctly decrypted text (which still has a layer of garble on it) from the doubley-garbled text. And even if it could, decrypting text twice would still take more time, wouldn't it?

The only working brute force method I know of in modern public key encryption(AES, Two-fish and Serpent) is trying every key. There is no readability is any part of the encrypted text because the relationship is based on weird relationships between prime numbers. I don't know the math behind it but so far no one has publicly revealed a way to decrypt the text without the original knowledge behind the keys or trying every combination(which is practically impossible in the larger bit keys).

 

[Wiccan_Child]

Yes and No. Yes because you have to factor two keys instead of one. No because at that point the passphrase is usually the weakest link because with it you have both keys.

The only working brute force method I know of in modern public key encryption(AES, Two-fish and Serpent) is trying every key. There is no readability is any part of the encrypted text because the relationship is based on weird relationships between prime numbers. I don't know the math behind it but so far no one has publicly revealed a way to decrypt the text without the original knowledge behind the keys or trying every combination(which is practically impossible in the larger bit keys).

My understanding of encryption (which may be entirely wrong) is that a formula converts one block of text into another, depending on some input value (i.e., the password). Different passwords cause the text to convert to different blocks of text, and the right passwords converts it to legible text. So, a brute force method of decryption must have some way of recognising when it's actually found the right password - i.e., it's readable text, not garbled nonsense. So double-encryption

Of course, if it can recognise the correct password without having to read the text, problem solved

 

[Biologist]

My understanding of encryption (which may be entirely wrong) is that a formula converts one block of text into another, depending on some input value (i.e., the password). Different passwords cause the text to convert to different blocks of text, and the right passwords converts it to legible text. So, a brute force method of decryption must have some way of recognising when it's actually found the right password - i.e., it's readable text, not garbled nonsense. So double-encryption

Of course, if it can recognise the correct password without having to read the text, problem solved

Brute forcing the keys means factoring the public key and regenerating the private key. No password needed.

 

[Wiccan_Child]

Brute forcing the keys means factoring the public key and regenerating the private key. No password needed.

Public and private keys hurt my head What do they do again?

 

[Biologist]

Public and private keys hurt my head What do they do again?

Here's what they are:

Take two large prime numbers call them p and q. Multiply them together and get pq which equals the modulus.

Take two large integers call them e and d. E will be public and you will keep d to yourself. Both must be smaller than (p-1)(q-1) and these will be your exponents. Let c be the encrypted text of the message m use e and the exponent to encrypt to message in the following way:

pq = one of the public parts of your key
e = public exponent
d = private exponent
m = your message
c = encrypted message
m^e mod pq = c
c^d mod pq = m

This works because the functions to create c and m are inverse. However, I'm not capable of demonstrating that anymore.

The purpose of public key encryption is to make it to where only one party knows how to decrypt the message but everyone in the world can know how to encrypt the message without it's integrity being compromised. This is different from previous cryptography methods where both the sender and receiver knew how to make and break a code. The only mathematical flaw in public key encryption is that e and d can be recomputed by factoring pq. However, factoring pq if p and q are made up of very large numbers could take many times the age of the universe(like 13 billion trillion trillion trillion years if you have a computer that's a trillion times faster than the number one super computer.)

 

[Michael]

Public and private keys hurt my head What do they do again?

Most modern encryption/decryption routines use a private or public "key" to secure the data in question so that the encryption/decryption method itself can be shared with everyone, but only someone with the correct 'key' can actually decrypt the data. One encryption method can then support a lot of unique "keys". It's like having different combination options so that you can have a unique code that only you know even though everyone has the same kind of lock.

 

[Michael]

My understanding of encryption (which may be entirely wrong) is that a formula converts one block of text into another, depending on some input value (i.e., the password). Different passwords cause the text to convert to different blocks of text, and the right passwords converts it to legible text. So, a brute force method of decryption must have some way of recognising when it's actually found the right password - i.e., it's readable text, not garbled nonsense. So double-encryption

Of course, if it can recognise the correct password without having to read the text, problem solved

You got it.

 

[GrowingSmaller]

You have left me for dead regarding the physical concept of symmetry. Help me catch up without too much intellectual effort, please.

 

[Wiccan_Child]

You have left me for dead regarding the physical concept of symmetry. Help me catch up without too much intellectual effort, please.

I tried reading the Wikipedia article on symmetry, but it just hurt my head.

 

[dewaddict84]

Question.
If you encrypt an encrypted file would that make it even harder to crack ?

Yes and No. Yes because you have to factor two keys instead of one

No. If you run encryption on a file twice, then you can still bruteforce a key just once. It literally makes a third key, which is made out of the two keys you used to encrypt it, which no-one knows about. If you have both keys, you could probably do some funky math and figure out what the third key is.

Double encrypting has uses when you want two different parties to need each others keys to get the cleartext. Like a message to estranged sons, who have to come together to read their father's last will and testament.

 

[AV1611VET]

I saw this on Jeopardy:

What can be 1/2 inch in width and as long as 4 miles?

 

[Wiccan_Child]

I saw this on Jeopardy:

What can be 1/2 inch in width and as long as 4 miles?

Human intestines? A worm or fungus? An arbitrarily sectioned strip of earth ?

 

[AV1611VET]

Human intestines? A worm or fungus? An arbitrarily sectioned strip of earth ?

I forget the category -- meteorology, I think.

 

[Wiccan_Child]

I forget the category -- meteorology, I think.

A raindrop? A tornado?

Do you actually know the answer?

 

[Cabal]

I tried reading the Wikipedia article on symmetry, but it just hurt my head.

Noether's theorem is pretty sweet though. Physical symmetry => conservation law.

 

[Wiccan_Child]

Noether's theorem is pretty sweet though. Physical symmetry => conservation law.

I learned about this at uni, it was very cool indeed. Science yay science!

 

[GrowingSmaller]

I tried reading the Wikipedia article on symmetry, but it just hurt my head.

We have to fight irreligion somehow!