Client-side encryption

Client-side encryption is the cryptographic technique of encrypting data on the sender's side, before it is transmitted to a server such as a cloud storage service.^[1] Client-side encryption features an encryption key that is not available to the service provider, making it difficult or impossible for service providers to decrypt hosted data. Client-side encryption allows for the creation of applications whose providers cannot access the data its users have stored, thus offering a high level of privacy.^[1]

Applications utilizing client-side encryption are sometimes marketed under the misleading or incorrect term "zero-knowledge",^[2] but this is a misnomer, as the term zero-knowledge describes something entirely different in the context of cryptography.

Client-side encryption seeks to eliminate the potential for data to be viewed by service providers (or third parties that compel service providers to deliver access to data), client-side encryption ensures that data and files that are stored in the cloud can only be viewed on the client-side of the exchange. This prevents data loss and the unauthorized disclosure of private or personal files, providing increased peace of mind for its users.^[1]

Current recommendations by industry professionals as well as academic scholars offer great vocal support for developers to include client-side encryption to protect the confidentiality and integrity of information. ^{[3][4] [5]}

• Tresorit^[6]
• MEGA^[7]
• Cryptee^[8]
• Cryptomator^[9]

• Apple iCloud offers optional client-side encryption when "Advanced Data Protection for iCloud" is enabled.^[10][11]
• Google Drive,^[12] Google Docs,^[12] Google Meet,^[13] Google Calendar,^[13] and Gmail^[13] — However, as of Jul 2024, optional client-side encryption features are only available to paid users.^[14]

• Dropbox^[15]

• SpiderOak Backup^[16]

• End-to-end encryption – the encryption of data between two different clients that are communicating with each other
• Homomorphic encryption