DocuSign Envelope ID: 39E02801-8AB7-44BC-906F-BCBEAC89CB11Schellman & Company, LLC
4010 W Boy Scout Boulevard
Suite 600
Tampa, Florida 33607
Tel:Fax:

1.866.254.0000
1.866.971.7070

Zscaler, Inc.
120 Holger Way
San Jose, CA 95134

January 22, 2021

RE: FEDERATION ASSURNACE LEVEL (FAL) 2 AND 3 CLARIFICATION FOR ZSCALER

To Whom It May Concern:
As you know, Schellman has performed testing as part of Zscaler’s FedRAMP efforts including both theZscaler Private Access (ZPA) and Zscaler Internet Access (ZIA) platforms.
It is my understanding that your customer has requested additional information surrounding encryption for
the Security Assertion Markup Language (SAML) assertions in accordance with the digital identity
requirements outlined in the National Institute of Standards and Technology (NIST) 800-63C.
Section 6.2.3 of NIST 800-63C states the following:
6.2.3 Encrypted Assertion
When encrypting assertions, the IdP SHALL encrypt the contents of the assertion using either theRP’s public key or a shared symmetric key. Shared symmetric keys used for this purpose by the IdPSHALL be independent for each RP to which they send assertions, and are normally establishedduring registration of the RP. Public keys for encryption MAY be fetched by the IdP in a secure
fashion at runtime, such as through an HTTPS URL hosted by the RP.
All encryption of assertions SHALL use approved cryptography.
When assertions are passed through third parties, such as a browser, the actual assertion SHALL beencrypted. For example, a SAML assertion can be encrypted using XML-Encryption, or an OpenID
Connect ID Token can be encrypted using JSON Web Encryption (JWE). For assertions that arepassed directly between IdP and RP, the actual assertion MAY be encrypted. If it is not, the assertion
SHALL be sent over an authenticated protected channel.
Note: Assertion encryption is required at FAL2 and FAL3.
When performing FedRAMP assessments, Schellman tests encryption of the SAML assertions (whenconfigured) as well as the encryption enforced at the transport layer for customer access paths that includes
protections for SAML assertions that are exchanged between the IdP (customer managed identity provider)and RP (Relying Party).
For the latter, if the RP (Zscaler in this case) enforces encryption at the transport layer for customer accesspaths using TLS 1.2, the test case is accepted. This supports the above guidance around “If the actualassertion is not encrypted, the assertion SHALL be sent over an authenticated protected channel.” Testing
performed through third-party tools and configuration reviews of protocols allowed server side, confirmed

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Zscaler’s enforcement of TLS 1.2. In addition, Zscaler requires the SAML assertion responses to be signed.
X509 certificates embedded within the SAML metadata files serve as the trust anchors allowing theverification of signatures, thus establishing trust in the SAML assertions that have been exchanged.
Additionally, Zscaler employs several FIPS 140-2 validated cryptographic modules in the federal
environment such as the Zscaler Crypto Module (CMVP#3159), Zscaler Mobile Cryptographic Module(CMVP #3154), and the Zscaler Java Crypto Module (CMVP #3188) used for enhancing the security ofcustomer data in transit paths. Critical software such as the Client Connector (formerly known as Z App)
rely on the embedded FIPS 140-2 validated modules for establishing secure connections.
This letter is supplemental to the FedRAMP assessment performed by Schellman. The information
provided in this document is “AS IS” without warranties of any kind. Schellman expressly disclaims anywarranties of representations including implied warranties and fitness for a particular purpose.
Please notify Zscaler if you require any further information.

Sincerely,

Douglas W. Barbin, CPA, CISSP, PCI QSA
Principal and Engagement Leader

About Schellman
Schellman & Company, LLC is a leading provider of attestation and compliance services. We are the only company in the world thatis a CPA firm, a globally licensed PCI Qualified Security Assessor, an ISO Certification Body and a FedRAMP 3PAO. Renowned forexpertise tempered by practical experience, Schellman’s professionals provide superior client service balanced by steadfastindependence. Our approach builds successful, long-term relationships and allows our clients to achieve multiple complianceobjectives using a single third party assessor.
Schellman serves hundreds of clients each year, including many Fortune 1000 and publicly traded companies. For further information,please visit http://www.schellman.com/ .