"A form of electronic authentication of a digital document. Digital signatures are created and verified using public key cryptography and serve to tie the document being signed to the signer." (J P Getty Trust, "Introduction to Metadata" 2nd Ed., 2008)
"Data which proves that a document, message, or other piece of data was not modified since being processed and sent from a particular party." (Mark S Merkow & Lakshmikanth Raghavan, "Secure and Resilient Software Development", 2010)
"cryptographic transformations of data that allow a recipient of the data to prove the source (non-repudiation) and integrity of the data." (Manish Agrawal, "Information Security and IT Risk Management", 2014)
"Data that is appended to a message, made from the message itself and the sender’s private key, to ensure the authenticity of the message" (Nell Dale & John Lewis, "Computer Science Illuminated" 6th Ed., 2015)
"Ensuring the authenticity and integrity of a message through the use of hashing algorithms and asymmetric algorithms. The message digest is encrypted with the sender’s private key." (Adam Gordon, "Official (ISC)2 Guide to the CISSP CBK" 4th Ed., 2015)
"A means of authenticating that a message or data came from a particular source with a known system identity." (O Sami Saydjari, "Engineering Trustworthy Systems: Get Cybersecurity Design Right the First Time", 2018)
"An electronic signature based upon cryptographic methods of originator authentication, computed by using a set of rules and a set of parameters such that the identity of the signer and the integrity of the data can be verified." (Shon Harris & Fernando Maymi, "CISSP All-in-One Exam Guide, 8th Ed", 2018)
"An encrypted means of identification that cannot be forged and that enables clients to validate servers and vice versa." (Microfocus)
"The combination of the private key, public key, message and hashing generates a digital signature. A digital signature is unique for every transaction and is a way to prove that the originator of the message has access to the private key." (AICPA)
