The foregone conclusion doctrine also is something folks should know about.
"while the content was itself not protected, the act of production could be testimonial irrespective of the content. The court reasoned, “[t]he act of producing evidence in response to a subpoena nevertheless has communicative aspects of its own, wholly aside from the contents of the papers produced. Compliance with the subpoena tacitly concedes the existence of the papers demanded and their possession or control by the taxpayer.” The court thus recognized that, in some instances, the Fifth Amendment protects the act of production.
Despite the act of production principle, the court in Fisher reasoned that “[t]he existence and location of the papers are a foregone conclusion, and the taxpayer adds little or nothing to the sum total of the Government's information by conceding that he, in fact, has the papers. Under these circumstances ... ‘no constitutional rights are touched. The question is not of testimony, but of surrender.’” This is referred to as the “foregone conclusion” exception to the “act of production” doctrine. In short, the Fifth Amendment is not implicated if the government knows of the existence, possession and authenticity of incriminating evidence, because the production thereof contains no testimonial import. Both the act of production and foregone conclusion doctrines are important to our understanding of how the Fifth Amendment protects against the compelled production of our passwords"
"while the content was itself not protected, the act of production could be testimonial irrespective of the content. The court reasoned, “[t]he act of producing evidence in response to a subpoena nevertheless has communicative aspects of its own, wholly aside from the contents of the papers produced. Compliance with the subpoena tacitly concedes the existence of the papers demanded and their possession or control by the taxpayer.” The court thus recognized that, in some instances, the Fifth Amendment protects the act of production.
Despite the act of production principle, the court in Fisher reasoned that “[t]he existence and location of the papers are a foregone conclusion, and the taxpayer adds little or nothing to the sum total of the Government's information by conceding that he, in fact, has the papers. Under these circumstances ... ‘no constitutional rights are touched. The question is not of testimony, but of surrender.’” This is referred to as the “foregone conclusion” exception to the “act of production” doctrine. In short, the Fifth Amendment is not implicated if the government knows of the existence, possession and authenticity of incriminating evidence, because the production thereof contains no testimonial import. Both the act of production and foregone conclusion doctrines are important to our understanding of how the Fifth Amendment protects against the compelled production of our passwords"
https://www.lawfareblog.com/fifth-amendment-decryption-and-b...