Comment Re:What I want (Score 1) 554
If the police can demand a decryption key, then presumably they can legally demand actual decryption. E.g., if you encrypt with an algorithm for which they have no software (maybe one you invented yourself), then I suspect that they can demand that you provide the plaintext, not just the key.
If the police may demand plaintext, then they can probably demand that the plaintext data be rendered into a form intelligible to humans. A non-technical person might not distinguish the decryption from the rendering, and therefore it's possible that the law might be interpreted this way even if the wording is specific to encryption. Therefore any attempt to conceal or destroy the data would be legally equivalent to refusing to provide the encryption key.
IANAL and haven't read the text of the relevant UK act; it may not work like this. But if it does, then anyone with digital archives could be in deep shit. If you have data files you can't read because they're in a custom format and you lost the parser (and that's just about every science department of every university, for starters), then the authorities might consider them equivalent to a refusal to decrypt.
(This is speculative. Please tell me I'm wrong in this conclusion.)