What are blind signatures?

A blind signature is a cryptographic method that hides the content of a message while it is being signed. It’s often used when the sender wants to protect or conceal their identity. 

Understanding blind signatures

An International Workshop on Public Key Cryptography explains, “There are two main security requirements for blind signature schemes. First, the scheme should be blind. That is, a malicious signer should not be able to link the output of the final signature by the user to the individual interactions with the user…. Second, the scheme should be unforgeable. That is, an adversary, even if he can impersonate the user and interact freely with the signer, should not be able to produce signatures on messages except for those that the signer signed.”

Under this cryptographic method, the signer cannot see the message content at any point when providing their signature. The primary function is to maintain the privacy of a message's content while still providing a valid and verifiable signature. This technology is applied in various areas, including electronic voting and anonymous digital cash systems. 

How blind signatures work

• The message sender generates a blinding factor and uses it to obscure or blind the original message. 
• The sender transmits the message to the signer who cannot see the original content. 
• The signer applies their digital signature to the blinded message. 
• The signer sends the signed, still blinded message back to the original sender. 
• The sender removes the blinding factor from the signed message, revealing the original message. 
• The recipient or any third party can verify the signature on the original message confirming authenticity without knowing the original signer ever saw the content. 

The benefits of their use in healthcare

Patient anonymity

Blind signatures ensure that protected health information remains anonymous when it needs to be verified or approved by third parties. It helps promote both privacy and the efficiency of the administrative process.

Secure electronic consent

Patients can consent to medical procedures or data sharing without revealing their identity, which can assist in clinical trials or research studies where anonymity is necessary.

Privacy in health data exchange

In health data exchanges, blind signatures can share records without revealing patient identities. It allows for privacy while providing for effective data interoperability. 

Protection in prescription services

Blind signatures can be used to sign electronic prescriptions to keep the prescribing process secure and private. The pharmacist can then verify the authenticity of the prescription without the risk of unauthorized access. 

Related: HIPAA Compliant Email: The Definitive Guide

FAQs

What are digital signatures?

A tool to verify the authenticity and integrity of digital messages. 

What are electronic health records?

EHRs are digital versions of patients' paper charts.