Editing Encryption (section)

=== Integrity protection of Ciphertexts ===

Encryption, by itself, can protect the confidentiality of messages, but other techniques are still needed to protect the integrity and authenticity of a message; for example, verification of a [[message authentication code]] (MAC) or a [[digital signature]] usually done by a [[Hash function|hashing algorithm]] or a [[Pretty Good Privacy|PGP signature]]. [[Authenticated encryption]] algorithms are designed to provide both encryption and integrity protection together. Standards for [[cryptographic software]] and [[Hardware encryption|hardware to perform encryption]] are widely available, but successfully using encryption to ensure security may be a challenging problem. A single error in system design or execution can allow successful attacks. Sometimes an adversary can obtain unencrypted information without directly undoing the encryption. See for example [[traffic analysis]], [[Tempest (codename)|TEMPEST]], or [[Trojan horse (computing)|Trojan horse]].<ref>{{cite web|url=https://usa.kaspersky.com/internet-security-center/threats/trojans#.VV3oaWDTvfY|title=What is a Trojan Virus – Malware Protection – Kaspersky Lab US|date=3 October 2023 }}</ref>

Integrity protection mechanisms such as [[message authentication code|MACs]] and [[digital signature]]s must be applied to the ciphertext when it is first created, typically on the same device used to compose the message, to protect a message [[End-to-end principle|end-to-end]] along its full transmission path; otherwise, any node between the sender and the encryption agent could potentially tamper with it. Encrypting at the time of creation is only secure if the encryption device itself has correct [[Key (cryptography)|keys]] and has not been tampered with. If an endpoint device has been configured to trust a [[root certificate]] that an attacker controls, for example, then the attacker can both inspect and tamper with encrypted data by performing a [[man-in-the-middle attack]] anywhere along the message's path. The common practice of [[Transport Layer Security#TLS interception|TLS interception]] by network operators represents a controlled and institutionally sanctioned form of such an attack, but countries have also attempted to employ such attacks as a form of control and censorship.<ref>{{cite news|url=https://thehackernews.com/2019/07/kazakhstan-https-security-certificate.html|title=Kazakhstan Begins Intercepting HTTPS Internet Traffic Of All Citizens Forcefully|first1=Mohit|last1=Kumar|date=July 2019|publisher=The Hacker News}}</ref>