Norma Acosta on Encryption and the Fifth Amendment

Hard Disks, Encryption and the Fifth Amendment

Norma Acosta

"Self Incrimination and Cryptographic

"When does public security come before
fifth amendment rights?"

the Department of Justice's "Federal Guidelines for
Searching and Seizing Computers".


Encryption and the Fifth Amendment

Modern cryptography can make it virtually impossible to decipher
documents without the cryptographic key, thus making the
availability of the contents of those documents depend on the
availability of the key. I will examine the Fifth Amendments'
protection against compulsory production of the key.

Compulsory Production of Cryptographic Keys and
      the Fifth Amendment

Accessibility of Documents

The Fifth Amendment provides: No person shall be
        compelled in any criminal case to be a witness against

The USSC has narrowed the privilege so that it applies
        only if the act of producing papers or records has a
        self-incriminatory communicative or testimonial

If the act of handing over the papers is
        noncommunicative--if it neither reveals the
        existence of the document nor authenticates
        it--then the Fifth Amendment does not apply.

Only natural persons are protected by the Fifth
        Amendment, and only for papers that they both own
        and control.

Corporations can never claim the privilege, and
        neither can natural persons with regard to
        corporate records.

Once papers are handed to another, the legitimate
        expectation of privacy needed to maintain a claim
        under either the Fourth or Fifth Amendments

Can a key be "incriminating"?

Fifth Amendment analysis must focus on the disclosure
        of the cryptographic key on the assumption that the
        key is not written down.

The Fifth Amendment is interpreted to bar only the
        production of "testimonial information," so
        the protection of the Fifth Amendment
        extends only to an incriminating
        communication that might "itself, explicitly
        or implicitly, relate a factual assertion or
        disclose information."

A non-cryptographic key is physical evidence, not
        testimonial evidence.

A cryptographic key need not have testimonial content.

A key can be any word, phrase, or a series of
        randomly chosen digits.

Although the key has no testimonial content, a statement
        concerning the key is testimonial.

One unique property of a cryptographic key is that it
        creates communicative content.

Producing a cryptographic key gives the document a
        testimonial content by decrypting the
        document and returning it into plaintext.

Result: the compulsory production of the
        key is the compulsory creation of
        testimonial content. Without the key,
        the documents would not be useful as

Another unique property of a cryptographic key is that it
        can operate as a digital signature, thus
        authenticating a document.

The Scope of Immunity

Derivative Use Immunity

Definition: Immunity from any use, direct or
        indirect, of the compelled testimony and any
        information derived therefrom.

The federal government has suggested that it will
        seek to grant immunity as a tool for
        discovering encrypted documents.

  Does immunity extend only to the key
        or does it also cover the decrypted document
        produced by applying the key to the encrypted

Immunity as a result of unique properties of
        cryptographic keys

Creation of communicative content through

The production of a cryptographic key
        indirectly relates the material
        contained in the document decrypted
        with the cryptographic key and should
        therefore lead to immunity under the
        Fifth Amendment for the document
        produced with the key.

Because the key is a necessary link in the chain, it
        gives rise to immunity from documents with

Authentication through decryption

The Fifth Amendment precludes the
        compulsory authentication of

Authentication will be impossible without the key.


Back to the list of student paper topics

Back to the CCP home page