disclosure of crypto keys

[Bert-Jaap Koops]

 David Swarbrick <david@swarb.demon.co.uk> wrote:
> Is it still self incrimination to hand over existing evidence? I think
> there is a clear argument to say that the privilege against self
> incrimination prevents only a requirement to provide a new statement.
[snip]
> I suspect that the argument about the right against self-incrimination
> is a false trail.
Not quite. It is true that the privilege against self-incrimination 
prevents only the mandatory producing of "testimonial statements". US 
case law provides good guidance on this. Tax returns are not 
testimonial evidence (Fisher), nor are business documents (Doe) or an 
authorization (for a bank to disclose information) which the 
suspect was compelled to write (Doe II). However, the _act of 
producing_  may be testimonial and incriminating, if in handing 
something over the holder admits to possession of the document. Only 
if it is a foregone conclusion that the holder possess a document, 
is handing it over not testimonial. (Doe)
(By and large the same holds for European case law, as I read it.)

That is why I conclude that handing over a crypto key is compatible 
with the privilege only if there is sufficient evidence ("a foregone 
conclusion") that the suspect has got the key and knows the 
passphrase. Otherwise, the _act of producing_ the key would testify 
to his knowledge of it.

Bert-Jaap