cryptography - CBC-MAC decryption, how MAC works in encryption -

-

i figured out triple des encryption , decryption credit card. can 1 tell me how de-crypt cbc-mac...cbc-mac @ end give 4 byte mac. mac encryption, how work? mac doing?

once there encryption done through cbc-mac, how can de-crypt them? triple-des not work case.

another question here. have heard of decryption algorithm involves:

  • dukpt
  • tdes, and
  • mac variant (versus pin variant)

i have understanding of tdes , dukpt, how mac variant play role in decryption algorithm?

how mac variant different pin variant?

thank you!

i figured out triple des encryption , decryption credit card. can 1 tell me how de-crypt cbc-mac...cbc-mac @ end give 4 bit mac.

here's visual of how cbc mode works via wikipedia. cbc mode via wikipedia

what cbc-mac take last block of ciphertext output , calls mac. mac should size of block cipher not 4 bits. if you're using 3des 64 bits.

from mac encryption, how work? mac doing?

mac , encryption 2 separate things. i'll try give brief rundown of each.

  • encryption provides confidentiality, means (in symmetric crypto case) correct key can read contents of message.
  • mac provides integrity, means message has not been tampered somewhere between sender , recipient.

the reason macs exist if cannot read encrypted messages, can still possibly modify encrypted message without recipient knowing modified (this has caused sorts of nasty problems in real world). mac send along encrypted message. recipient first compute mac of encrypted message, , checks if matches mac sent encrypted message. if match recipient knows message not tampered with.

once there encryption done through cbc-mac, how can de-crypt >them? triple-des not work case.

if using 3des encrypt recommend first encrypting message (let's call c). i'd recommend using other cbc-mac because cbc-mac not provide security. i'd recommend use hmac compute mac encrypted message (hmac(c)). means you'll need 2 keys, 1 3des , 1 hmac. hmac supported in languages finding implementation shouldn't issue.

so in summary, take message m, compute 3des(m) = c, compute hmac(c) = t, , send (c, t) whoever receiving data. recipient compute hmac(c) = t', check t' == t, , if match compute 3des(c) = m original message. hope helps, quite bit of info, feel free ask clarify. :)


Comments

Post a Comment

Popular posts from this blog

c# - Better 64-bit byte array hash -

-
i need hash algorithm produces 64-bit hash code ( long ) fewer collisions string.gethashcode() , fast (no expensive calls cryptographic functions). here's implementation of fnv still shows 3% of collisions after testing 2 million random strings. need number way lower. void main() { const string chars = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz!#@$%^&*()_+}{\":?><,./;'[]0123456789\\"; const int n = 2000000; var random = new random(); var hashes = new hashset<long>(); int collisions = 0; for(int = 0; < n; i++) { var len = random.next(chars.length); var str = new char[len]; (int j = 0; j < len; j++) { str[j] = chars[random.next(chars.length)]; } var s = new string(str); if(!hashes.add(get64bithash( s ))) collisions++; } console.writeline("collision percentage after " + n + " random strings: " + ((doubl
Read more

webrtc - Which ICE candidate am I using and why? -

-
[questions in bold below] i have setup kurento media server 5.1.3 in datacenter behind firewall running os ubuntu 14.04. has 2 network cards: 222.222.222.222 (eth0 - private ip) 111.111.111.111 (eth1 - public ip) attached below sdp (setremotedescription) when browser connected kurento media server type: answer, sdp: v=0 o=- 5487318114793304426 0 in ip4 0.0.0.0 s=kurento media server c=in ip4 0.0.0.0 t=0 0 a=group:bundle audio video m=audio 59068 rtp/savpf 111 0 c=in ip4 111.111.111.111 a=rtpmap:111 opus/48000/2 a=rtpmap:0 pcmu/8000 a=sendrecv a=rtcp:59068 in ip4 111.111.111.111 a=rtcp-mux a=ssrc:669011897 cname:user39019747@host-6e83e4c2 a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time a=mid:audio b=as:20 a=ice-ufrag:ymdk a=ice-pwd:lylifk5ueqzpwm91ddj37e a=fingerprint:sha-256 ff:0f:81:8c:41:4e:b4:b6:c6:d8:36:f3:d6:5f:09:fd:5f:af:13:b3:9d:fc:12:66:ac:f3:56:d6:5b:0a:73:5d a=candidate:1 1 udp 2013266431 111.111.111.111 55239 typ host a=candidate:2 1 udp
Read more

php - Zend Framework / Skeleton-Application / Composer install issue -

-
i trying create zend framework application using skeleton in netbeans. when run composer install, following error message: "c:\php\php.exe" "c:\composer\composer.phar" "--ansi" "--no-interaction" "update" "--dev" using deprecated option "dev". dev packages installed default now. loading composer repositories package information updating dependencies (including require-dev) requirements not resolved installable set of packages. problem 1 - package requires php >=5.5 php version (5.4.42) not satisfy requirement. problem 2 - installation request zendframework/zendframework 2.5.1 -> satisfiable zendframework/zendframework[2.5.1]. - zendframework/zendframework 2.5.1 requires php >=5.5 -> php version (5.4.42) not satisfy requirement. done. apparently, zend framework only needs php 5.3+ contradicts above. need use php 5.4. my composer.json following: { "name": "
Read more