A trusted entity that issues and revokes public key certificates.
Sources:
FIPS 201-3 under Certification Authority
NIST SP 1800-12b under Certification Authority
NIST SP 1800-16B under Certificate Authority from NISTIR 8149
NIST SP 1800-16D under Certificate Authority from NISTIR 8149
NISTIR 7711 under Certification Authority

  An entity authorized to create, sign, issue, and revoke public key certificates.
Sources:
CNSSI 4009-2015 under certification authority from CNSSI 1300 - Adapted

  Operations performed in defeating cryptographic protection without an initial knowledge of the key employed in providing the protection.
Sources:
NIST SP 800-57 Part 2 Rev.1 under Cryptanalysis

  The study of mathematical techniques for attempting to defeat cryptographic techniques and information system security. This includes the process of looking for errors or weaknesses in the implementation of an algorithm or of the algorithm itself.
Sources:
NIST SP 800-57 Part 2 Rev.1 under Cryptanalysis

  1. Operations performed to defeat cryptographic protection without an initial knowledge of the key employed in providing the protection. 2. The study of mathematical techniques for attempting to defeat cryptographic techniques and information-system security. This includes the process of looking for errors or weaknesses in the implementation of an algorithm or in the algorithm itself.
Sources:
NIST SP 800-57 Part 1 Rev. 5 under Cryptanalysis