Cybersecurity without encryption in today’s work environment is like hitting the beach mid-summer and forgetting your sunscreen… it’s a bad idea and you’re going to pay the consequence” says Jonathan Goetsch, CEO of US ProTech and ANAMO, a CDM Cybersecurity software development company.

There’s standard AES256 encryption, and then there’s Double Key Encryption (DKE). In the case of DKE encryption, it is the combination of two keys held by separate parties that encrypt or decrypt data. Recently, Microsoft announced the public preview of Double Key Encryption (DKE). To quote Microsoft:

Double Key Encryption enables you to protect your highly sensitive data while keeping full control of your encryption key. It uses two keys to protect your data—one key in your control, and a second key is stored securely in Microsoft Azure. Viewing data protected with Double Key Encryption requires access to both keys. Since Microsoft can access only one of these keys, your protected data remains inaccessible to Microsoft, ensuring that you have full control over its privacy and security.”

Is DKE right for my needs?

The real answer is “It depends.” It is intended for some super rare scenarios that very few clients have. There are serious productivity limitations to DKE that are nearly identical to HYOK, where many features inside Office 365 and other services will not function such as SharePoint Search, eDiscovery Search, Data Loss Prevention, Transport Rules, Exchange ActiveSync, Journaling, Malware scanning, Archiving Solutions and any other services that needs to read data such as 3rd party document management systems.

Your Client Key is hosted outside of Microsoft (wherever you want) via a web service that you are responsible for hosting. If your web service goes down (intentionally or unintentionally) then no new data can be encrypted or decrypted.

This is similar to its predecessor, Hold-Your-Own-Key (HYOK) which most agree DKE will eventually replace at some point in the future. Except there is one big advantage: Unlike HYOK, DKE does not depend upon on-premises Active Directory Rights Management Services (AD RMS). So it is a simpler configuration.

Therefore customers should carefully evaluate all key options before proceeding with DKE (see table below)

 

Encryption Key Comparison

HYOK

(Hold-Your-Own-Key)

Double-Key Encryption

(NEWEST)

BYOK
(Bring-Your-Own-Key)

Microsoft

Managed

Key

Can Microsoft Read the Encrypted Data?

No

No

Yes

Yes

AD RMS Required?

Yes

No

No

No

100%Cloud Hosted

No

No

Yes

Yes

On-Prem or Cloud
DMZ Req?

No

Yes

No

No

On-Prem
HSM Req?

Yes

Yes

Yes

No

ActiveSync Support

No

No

No

No

Exchange On-Premises IRM

No

No

Yes

Yes

Outlook Mobile

No

No

Yes

Yes

OWA

No

No

Yes

Yes

Office Mobile

(Word/Excel/PPT)

Yes

(Consume Only)

Yes

(Consume Only)

Yes

Yes

Mac OSX

Yes

(Consume Only)

Yes

(Consume Only)

Yes

Yes

SharePoint Search

No

No

Yes

Yes

Key Strength

RSA 2048-bit (Key Exchange)

AES 128 (Wrapping)

SHA 256 (Signing)

(FIPS 140-2)

RSA 2048-bit (Key Exchange)

AES 128 (Wrapping)

SHA 256 (Signing)

(FIPS 140-2)

RSA 2048-bit (Key Exchange)

AES 128 (Wrapping)

SHA 256 (Signing)

(FIPS 140-2)

RSA 2048-bit (Key Exchange)

AES 128 (Wrapping)

SHA 256 (Signing)

(FIPS 140-2)

External Collaboration

No

No

Yes

Yes

Office Client Support

Office 2013 +

Office Insider*

Office 2013 +

Office 2010 +

Auditing

Yes

Yes

Yes

Yes

 

Are there any downside?

What if I lose my key? Your data is inaccessible, and there is no ‘back door’ keys like the ‘Availability Key’ feature in BYOK that allows Microsoft to decrypt data if you lose your BYOK key.

Office Insider is required at the time of this writing, but eventually it will roll out to Office versions in mainstream support.

Initially at the time of this writing, the AIP Unified Labeling Client is required to encrypt/decrypt content. It will eventually be available natively in the Office Ribbon.

Additional Resources

Special thanks to Joe Stocker (MS/MVP) who provided material
Update [10/22/2020] Host DKE on IIS, using an on-premises server – Microsoft Tech Community