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    Cryptography Diffie–Hellman key exchange question

    April 05, 2019

    Cryptography Diffie–Hellman key exchange question

    Diffie–Hellman key exchange question

    Posted: 04 Apr 2019 05:07 PM PDT

    I am little bit confused about Diffie Hellman key exchange.I have done some fun with small numbers and find situations where computed key exchange and secret key has same result.This is one of them:

    var p = 10;// prime number - public var g = 6; // primitive root modulo p - public var alice_random_number = 4; // private var bob_random_number = 3; // private var ag = Math.pow(g,alice_random_number); var ap = ag % p;// Alice calculate ap and sends to Bob - public var bg = Math.pow(g,bob_random_number); var bp = bg % p;// Bob calculate bp and sends to Alice - public var abp = Math.pow(bp,alice_random_number); var asp = abp % p; // Alice calculate asp - private (shared secret to be used for future encryption) var bap = Math.pow(ap,bob_random_number); var bsp = bap % p; // Bob calculate bsp - private (shared secret to be used for future encryption) console.log(`const p,g: ${p},${g} public`); console.log(`ag,bg: ${ag},${bg} private`); console.log(`ap,bp: ${ap},${bp} public` ); console.log(`abp,bap: ${abp},${bap} private`); console.log(`secret key: ${bsp},${asp} private`); /* const p,g: 10,6 public ag,bg: 1296,216 private ap,bp: 6,6 public <---- computed exchange keys abp,bap: 1296,216 private secret key: 6,6 private <----- secret key result */

    ​

    By changing the constants (g or p) I get different results, but sooner or later I end up with secret leak in computed results (ap, bp).

    I am not cryptographer or mathematician, so sorry if I miss understand something.

    How important is what constant values are chosen for p and g and what should I know about their values?From what I know and what I do not, I would say that it is very possible that this happen in larger range (higher p value).

    EDIT:
    I just find out what prime number mean. :D
    So, that solves my confused mind.
    But I would like to know more about if there are and if possible to find some simple example of ecdsa example with simple small numbers like I found for key exchange on wiki page.

    https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange
    I am not used to math expressions like the these on wiki page for ecdsa.
    https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm

    submitted by /u/zninja-bg
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    Does state mean the data that's being worked on currently?

    Posted: 04 Apr 2019 11:41 PM PDT

    https://imgur.com/a/jPol9Bn

    I have no idea what state means. What does it mean by the adversary starts the hash function with t as it's internal state? like the first step? Please explain.

    submitted by /u/wwe20180
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    Discover Decryption Algorithm by Samples

    Posted: 04 Apr 2019 08:25 PM PDT

    Hello! I have a particular request that I couldn't successfully Google.

    I have a load of various encrypted files, some of which I also have the decrypted versions of. I was wondering if there is a tool that can compare an encrypted file to its decrypted counterpart and use that information to decrypt other files.

    If you would like, here are a few samples:

    I would be very grateful for any information that can be provided! (And I can provide more samples if necessary.)

    Edit: It's worth noting that the encryption is done by CypherTec, and the filesizes between encrypted/decrypted files don't change at all. The key(s) (and/or other such elements) are stored off-file, but are inaccessible to me.

    submitted by /u/LyritZian
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    I submitted here not knowing what the key was (Been in encryption course for 10 weeks) and now we are talking about key generation?

    Posted: 04 Apr 2019 09:44 PM PDT

    I did not know what a key was or where it even came from. Now we are talking about key generation/distribution. Is this common? When the semester first started he just would use the word key even though this whole time all I knew that it was a string of random bits of data.

    I just find it odd that we are now talking about it. I feel like we should of done it earlier.

    submitted by /u/Ownanteater6
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    Been getting some strange emails... One looks like it contains a cryptographic message.

    Posted: 04 Apr 2019 09:37 AM PDT

    Hi all,

    Ive been receiving some strange emails over the past two months. They are all formatted the same way, but aren't always sent from the same address. I tried to trace back the sender, but came up with nothing. The heading of the emails seem to be poorly written news stories. Some of the emails contain no content, or a link (which I haven't tried clicking on for obvious reasons). One of them however has a very long string of characters which looks like it could be some type of cryptography.

    ​

    Pastebin of cryptographic email: https://pastebin.com/8VqdSQcs

    Imgur of emails: https://imgur.com/a/h5NbTcX

    ​

    please let me know if you find anything. Thanks!

    submitted by /u/bwesty016
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