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8

Although x.509 is the standard for PKIs with CAs, different certificate formats have been defined for the other 2 major PKI approaches: SPKI has defined its own certificate format , still (forever?) in draft status. Web-of-Trust models usually use the OpenPGP certificate format defined in RFC2440 RFC4212 "Alternative Certificate Formats for the ...


4

To answer this question, we must have a look at how TLS/SSL works. I guess you know that the aim of TLS/SSL is to authenticate communicating parties before setting up an encrypted connection through which application data will flow. And as you may already know, an SSL handshake/session will use asymmetric crypto for authentication and session setup and ...


4

If you use public key crypto in the correct way, then every user has it's own private key and corresponding public key (included in the certificate) and the keys of users are not related. Consequently, compromising the private key of one user does not affect any of the other users. So in the case of compromise of the private key of one user the remaining ...


3

Card verifiable certificates (CVC) are rather important for smart card technologies. In general X509 certificates have a rather complex structure and may take a lot of room compared to the RAM and EEPROM/flash memory that is available in a smart card chip. It is certainly possible to parse an X509 certificate in a processor card (it's a generic processor, ...


2

Quote from http://www.digi-sign.com/node/10922 All Types of Digital Certificates Are Also a X509 Certificate A X509 certificate *refers to all types of digital certificates, regardless of how they are utilized, and implies the current standardization used to design and create digital certificates. This standardization recognizes that the ...


2

$ openssl genrsa | openssl rsa -text -noout Private-Key: (512 bit) modulus: 00:e7:be:c0:b7:7a:8a:e6:58:c3:dc:3e:eb:ed:bc: a7:15:04:78:8d:9d:fe:a2:83:aa:ca:85:5f:4b:ae: 5c:fa:3d:bd:2b:a9:91:58:e1:da:d8:8a:bd:25:6d: 07:10:74:52:2f:ee:ce:bd:3c:c6:89:01:2e:ff:9a: 3b:61:4d:e7:81 publicExponent: 65537 (0x10001) privateExponent: ...


2

Firstly, PKI makes use of a private key and a public key. The private key is known only to the user, while the public key is communicated securely via the use of certificates. To provide authentication and non-repudiation, users may sign a message with their private keys and obtain a digital signature. Any other users can verify that the signed signature is ...


2

Well, as it says in your link the problem is authentication. So somehow Alice and Bob must set up an authenticated channel. One way of implementing such a channel is by Alice and Bob holding each others public verification key for a signature scheme. A CA would probably not hold a secret key for Alice and Bob. However, using a CA to get an authentic copy ...


2

The last 2 numbers are the ecdsa signature, it is two unsigned integers, when the highest byte happens to be larger than 127, the asn.1 BER encoding adds an extra zero.


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The question Alex linked in comments explains why authentication works to prevent a man-in-the-middle attack on Diffie–Hellman. So, whenever you can do the key exchange in an authenticated channel, you can be sure there is no MitM attack. (Assuming DH problem remains unbroken, of course.) Now, your questions: Is one solution for both Alice and Bob ...


1

The problem about Man-in-the-Middle attack on Diffie-Hellman is that both sides are not confident about other side's public key (g^a and g^b). If they were sure that they have correct public key of their's friend Man-in-the-Middle attack wouldn't be possible, because MITM attack is based on the forgery of public keys by adversary! If for instance Bob and ...


1

I am a graduate student researching cryptography at JHU. If you want to research cryptography in academia, you'd better have a strong ability in mathematics. In my opinion, programming is a basic ability and software is just a kind of tool to realize your idea. cryptographers who made breakthroughs before all have a strong mathematics and theoretical ...


1

No, in general re-using keys is not advisable. Even if you would have a secure token then it would be better to have multiple keys stored in it. In general the level of security required for certificate authorities is higher than the security required for personal use of a key. If you later want to your CA key within a smart card or HSM then it should also ...


1

In Kerberos, if the Key Distribution Center is compromised then all the stored keys are exposed. In PKI, if a Certificate Authority is compromised then certificates may be forged. So, I guess we typically assume that the "trusted" third party will not be compromised so easily? Because either method you choose, there are still some inherent risks.



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