ccna before ccent

ccna before ccent.7.4.2.4 Digitally Signed CodesIn addition to ensuring the authenticity and integrity of messages, digital signatures are often used to guarantee the authenticity and integrity of mobile and typical software code. An executable file or a complete installation package of a program is wrapped in an envelope using a digital signature, which allows the end user to verify the signature before installing the software.Digitally signed code provides the following assurances about the code. The code has not been modified since it left the software publisher.7.4 Public Key Cryptography 209That the code is authentic and did originate from the publisher. The publisher has undeniably released the code. This provides non-repudiation for the release. A digital signature can only be forged if someone has access to the publisher's private key. If the key is properly protected, the digital signatureThe assurance level of a name is very high. The user of the software must also be given the public key used to verify the signature. The user can obtain the key in a secure manner. For example, the key can be included in the installation of the operating system or securely transmitted over the network. When using digital signatures, the most important thing is to protect the private key. If an entity's signing key is compromised, an attacker will be able to sign data in the entity's name without the user being able to deny it. To exchange authentication keys in a scalable manner, a secure and feasible method must be adopted.7.4.2.5 Digital Signature AlgorithmsWell-known asymmetric algorithms, such as RSA or the DigitalSignatureAlgorithm (DSA), are often used to perform digital signatures.DSAIn 1994, NIST chose DSA as the Digital Signature Standard (DSS). DSA is based on the discrete logarithm problem and can only provide digital signatures.