| C14N | CanonicalizatioN |
| CA | Certificate Authority |
| CATT | Center for Advanced Technology in Telecommunications |
| CBC | cipher block chaining |
| CBR | call-by-reference |
| CBV | call- by-value |
| CD-ROM | Compact disk “read-only memory |
| CGI | Common Gateway Interface |
| CICS | Customer Information Control System |
| CMP | Certificate Management Protocol |
| CMP | container-managed persistence |
| CN | Common Name |
| COBOL | Common Business Oriented Language |
| COM | Component Object Model |
| CORBA | Common Object Request Broker Architecture |
| CPU | central processing unit |
| CRL | certificate revocation list |
| CRT | Chinese Remainder Theorem |
| CSI | Common Secure Interoperability |
| CSIv2 | CSI Version 2 |
| CSP | cryptographic service provider |
| CSR | Certificate Signing Request |