CMMC Practice SC.L2-3.13.8 – Data in Transit: Implement cryptographic mechanisms to prevent unauthorized disclosure of CUI during transmission unless otherwise protected by alternative physical safeguards.
Links to Publicly Available Resources
Discussion [NIST SP 800-171 R2]
This requirement applies to internal and external networks and any system components that can transmit information including servers, notebook computers, desktop computers, mobile devices, printers, copiers, scanners, and facsimile machines. Communication paths outside the physical protection of controlled boundaries are susceptible to both interception and modification. Organizations relying on commercial providers offering transmission services as commodity services rather than as fully dedicated services (i.e., services which can be highly specialized to individual customer needs), may find it difficult to obtain the necessary assurances regarding the implementation of the controls for transmission confidentiality. In such situations, organizations determine what types of confidentiality services are available in commercial telecommunication service packages. If it is infeasible or impractical to obtain the necessary safeguards and assurances of the effectiveness of the safeguards through appropriate contracting vehicles, organizations implement compensating safeguards or explicitly accept the additional risk. An example of an alternative physical safeguard is a protected distribution system (PDS) where the distribution medium is protected against electronic or physical intercept, thereby ensuring the confidentiality of the information being transmitted.
The intent of this practice is to ensure CUI is cryptographically protected during transit, particularly on the internet. The most common way to accomplish this is to establish a TLS tunnel between the source and destination using the most current version of TLS. This practice does not specify a mutually authenticated handshake, but mutual authentication is the most secure approach to creating a tunnel.
When CMMC requires cryptography, it is to protect the confidentiality of CUI. FIPS-validated cryptography means the cryptographic module has to have been tested and validated to meet FIPS 140-1 or-2 requirements. Simply using an approved algorithm is not sufficient –the module (software and/or hardware) used to implement the algorithm must be separately validated under FIPS 140. Accordingly, FIPS-validated cryptography is required to meet CMMC practices that protect CUI when transmitted or stored outside the protected environment of the covered contractor information system (including wireless/remote access). Encryption used for other purposes, such as within applications or devices within the protected environment of the covered contractor information system, would not need to be FIPS-validated.
This practice, SC.L2-3.13.8, requires cryptographic mechanisms be used to prevent the disclosure of CUI in-transit and leverages SC.L2-3.13.11, which specifies that the algorithms used must be FIPS-validated.