I'm trying to compare the key establishment protocol i'm working on with others already proposed but i am not able to find any research papers in which symmetric pairwise keys are established using public key cryptography. Can anyone suggest a list of research papers available on the web for free?
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Recently, I was pointed to a post from 2011 by a friend, which described Google's move towards forward secrecy. From what I understand, the essence of forward secrecy seems to lie in the fact that the private keys are not kept in persistant storage.
I have various doubts about how something like this could be implemented.
What if the server goes down without warning - do the key pairs have to be regenerated? Does the public key have to be signed again to create another certificate?
Could someone point me to posts/pdfs where the implementation of something like this is described. Suggested reading resources?
Are you aware of anyone else that has implemented forward secrecy? Have you tried something similar at your workplace?
Thanks!
In Forward Secrecy, there are still long-term keys. The only implication is, that the compromisation of a long-term key will not allow an attacker to compromise temporary session keys, when the long-term key has changed. This means that a long-term key must not be derived from another (older) key.
Here is a good survey on this topic.
According to Wikipedia:
PFS is an optional feature in IPsec (RFC 2412).
SSH.
Off-the-Record Messaging, a cryptography protocol and library for many instant messaging clients, provides perfect forward secrecy as well as deniable encryption.
In theory, Transport Layer Security can choose appropriate ciphers since SSLv3, but in everyday practice many implementations refuse to offer PFS or only provide it with very low encryption grade.
In TLS and many other protocols forward secrecy is provided through the Diffie-Hellman (DH) algorithm. Vanilla DH is rather simple and provides perfect forward secrecy if the exponents are randomly generated each time, but provides no authentication. Therefore in TLS it is using in combination with a signature algorithm, usually RSA.
TLS provides many ciphersuites that support PFS and many that do not. Most TLS clients support PFS but many servers do not, because it is thought that PFS takes too much CPU.
Team,
I would like to have asymmetric encryption using AES algorithm for iPhone application using Objective C.
I have widely seen symmetric encryption using AES, so im not sure about the support for asymmetric encryption with AES. Kindly suggest me on this.
AES is a symmetric cipher. It can't simply be used an an asymmetric (i.e., public-key) capacity.
I am guessing the reason for your question is the issue of key exchange - such that you can establish an AES-encrypted connection without having to rely on a pre-shared key.
Numerous valid approaches exist, but I'll just hit on two:
Take a look at or Diffie-Hellman. You can get both sides of a connection to agree on a key without actually having to exchange that key. http://en.wikipedia.org/wiki/Diffie–Hellman_key_exchange
RSA. I'm a fan of Botan. It's free. It works. You can generate public/private key pairs on both sides, exchange the public keys, then securely exchange private keys, and then start AES. http://botan.randombit.net/pubkey.html
As always, this advice needs to be accompanied with a warning: it's very easy to do this incorrectly and largely (or entirely) thwart your security efforts. Tread carefully.
Does anybody know some simple authentication and data transfer protocol based on symmetric keys only? Due to memory constraints (kilobytes RAM and ROM) we cant afford asymmetric cryptography and due to closed environment asymmetric cryptography does not increase security of any way.
I am looking for simple symmetric cryptography protocol that can be kept in head and written on one paper sheet. I was looking in EAP-PSK https://www.rfc-editor.org/rfc/rfc4764#page-4 but still think that 2^6 pages is way to much for something simple and secure.
Does anybody know some useful url, paper or idea?
For secrecy, use AES-CBC. For message authentication, use HMAC-SHA256. Use a different key for each.
In both cases, use an existing, validated, timing-attack-free implementation of the cryptographic primitives.
I think you're looking for the Diffie-Hellman key exchange: only requires bignum integer arithmetic (powers, multiplication, and modulus only, at that): http://en.wikipedia.org/wiki/Diffie–Hellman_key_exchange
I need to fully understand the IPSec Phase 1 negotiation.
now, I break this to 3 steps:
Algorithm negotiations
Key Exchange Data
Identification
I'm using Wireshark to investigate the process and so far I fully understand the first part (Algorithm Negotiations).
My current problem lies in the 2nd part: Key Exchange Data.
The algorithms in use are AES-CBC-256bit, Pre-shared key, MD5 & 1024 bit Group.
The "ISAKMP Payload"->"KeyExchange Payload"->"KeyExchangeData" is beyond me...
I have no clue what it is.. an MD5'ed pre-shared key? Is it encrypted?
See draft-kivinen-ipsecme-ikev2-minimal-01. It does a pretty good job explaining on what is needed for IKEv2 protocol
ISAKMP / IKEv1 / IPSec phase 1 is a bit more complicated, but most things in IKEv2 are somewhat analogous to the older version - and certainly help in learning the more complex stuff.
Key exchange data in the KE payload is just the Diffie-Hellman "shared secret". If you are literate with python code, see this project. There is also a module that can do the math and has some of the most used DH group's primes.
This page should help to understand IPSec.
I am a newbie in cryptographic system but i have seen many sources tell that
even the good algorithm and good key is not enough,
i have a little confuse why is that?
Possibly not enough because in the game of cryptography there is also the trust part.
Anyway, check out this article: Security Pitfalls in Cryptography
http://en.wikipedia.org/wiki/Cryptographic_engineering
There are two basic kinds of encryption algorithms in use today:
Private key cryptography, which uses the same key to encrypt and decrypt the message. This type is also known as symmetric key cryptography.
Public key cryptography, which uses a public key to encrypt the message and a private key to decrypt it. The name public key comes from the fact that you can make the encryption key public without compromising the secrecy of the message or the decryption key. Public key systems are also known as asymmetric key cryptography.
http://www.amazon.com/Applied-Cryptography-Protocols-Algorithms-Source/dp/0471117099
. This book is nice one regarding this
Algorithms
http://hell.org.ua/Docs/oreilly/tcpip/puis/ch06_04.htm
U can read this patent is talking about US Patent 6769062 - Method and system of using an insecure crypto-accelerator
http://www.patentstorm.us/patents/6769062/claims.html
Read this http://www.schneier.com/essay-028.html
Your question is vague, but I'll add an aspect that is important: The users handling of the key and understanding of the system. Cryptography does in a way move the target from the communication to the sender or recipient.
Also, the algorithms quality is only halfway there - the implementation of the algorithm can introduce unforseen security issues.
The security of a system depends on many factors, only one of which is the cryptosystem of choice.
Modern symmetric (e.g. AES) and asymmetric (e.g. RSA) cryptosystems are very secure (read: practically impossible to break) in themselves, but the way you use the cryptosystem, and user behavior changes everything.
I've always argued that even the most basic cryptographic tasks should be done, or at least supervised, by cryptography experts, and Jeff has recently proved me right.
If you have had no formal education on cryptography, please seek professional advice from an expert.