Category: IT Certification Exams
ECDSA algorithms – Digital Signatures
9.4.3 ECDSA algorithms The ECDSA algorithms ecdsa˙secp256r1˙sha256, ecdsa˙secp384r1˙sha384 as well as ecdsa˙secp521r1˙sha512 are defined in the American National Standards Institute (ANSI) X9.62 standard [6]. The corresponding elliptic curves are defined in the ANSI X9.62 and FIPS 186-4 [128] standards, and the hash functions are defined in the FIPS 180-4 standard [129]. We already learned how…
Explore MoreEdDSA algorithms 2 – Digital Signatures
The points on the elliptic curve form a group under addition, that is: The neutral element for this group is (0,1). The explicit formulas for computing the points x3 and y3 are and Unlike with many other elliptic curves, these formulas have the advantage of being complete. That means they are valid for all points…
Explore MoreEdDSA algorithms – Digital Signatures
9.4.4 EdDSA algorithms The ed25519 and ed448 algorithms are instantiations of the Edwards-Curve Digital Signature Algorithm (EdDSA) with the elliptic curves edwards25519 and edwards448, respectively. The algorithms are defined in RFC 8032 Edwards-Curve Digital Signature Algorithm (EdDSA). The ed25519 algorithm offers roughly 128-bit security. This is in line with the security level recommended by common…
Explore MoreWhat is a digital certificate? – Digital Certificates and Certification Authorities
10.1 What is a digital certificate? Remember from Chapter 7, Public-Key Cryptography, that public keys, more precisely their numerical representation and their relation to a certain entity, must be authentic. Otherwise, an attacker, Eve, might exchange her own public key with Alice’s and could read Alice’s messages. Digital signatures, on the other hand, create the…
Explore MoreMinimum data fields 2 – Digital Certificates and Certification Authorities
Note that the above Critical/Not Critical classification might differ from the guidelines of the Certification Authority Browser Forum (CA/Browser Forum), a consortium of certification authorities, web browser vendors, and companies providing PKI-based applications. The CA/Browser Forum guidelines govern the issuing and management of X.509v3 certificates, including those used for TLS [43]. Figure 10.2 shows some…
Explore MoreMinimum data fields – Digital Certificates and Certification Authorities
10.2.1 Minimum data fields According to X.509v1, a digital certificate has to contain at least the following eight data fields: Figure 10.1 shows some of these minimum data fields for the certificate of the web server www.amazon.com within Google Chrome’s certificate viewer. Figure 10.1: X.509v3 certificate of www.amazon.com as shown by Google Chrome’s certificate viewer…
Explore MoreEnrollment – Digital Certificates and Certification Authorities
10.2.3 Enrollment The process by which Alice obtains a certificate from a CA is called enrollment. There are various options for doing this, but in the most common scenario, Alice first computes a key pair (PKAlice,SKAlice). She then generates a Certificate Signing Request (CSR) and sends it to the CA. The CSR is signed by…
Explore MoreOnline Certificate Status Protocol (OCSP) – Digital Certificates and Certification Authorities
10.2.5 Online Certificate Status Protocol (OCSP) An alternative to CRLs is to use an Online Certificate Status Protocol (OCSP) [110] server, as indicated in the Authority Information Access certificate extension. Compared to CRLs, OCSP provides a more timely revocation information. An OCSP client can transmit a status request for a specific digital certificate to an…
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