If any encrypted data could be decoded within a day (or shorter, to the point of hours, given enough computing power and weak encryption), all wireless transmissions may be intercepted, and all copper/fiber cables in networks may be tapped, what effects would that have on daily life in a digitally-connected world, and how would people live with it?
For background, this idea came up as a moderately hard-ish science explanation for why courier transport of documents and data-containing devices (flash/hard drives etc.), and face-to-face meetings would make sense in a cyberpunk-style megacity.
A few things I've considered based on the premise:
Airgapping any critical system/intranet, thus the reliance on physical transfers for secure communications. (Anything implanted inside one's head is a very 'critical system', so I don't think anyone would go for a wifi/bluetooth-enabled implant. I may be wrong.)
Electronic banking being done via One-Time Pad encrypted transactions, where even if a transmission is decrypted after the fact, it only gives information about what the transaction was (parties, amount, etc.), but not the information necessary to spoof the next transaction. This would necessitate physically visiting the local bank to get new one-time codes every so often. (Like getting a new book of paper checks.)
For networked systems, a focus on intrusion prevention via blocking ports completely and lockout after very few attempts, rather than the encryption/token based trust systems of today such as SSL, ADFS, PGP, etc. Probably compartmentalizing at an OS level even more than modern OSs, so any process that has a network connection is effectively sandboxed from the rest of the device ('hard drive'/permanent storage write access, particularly) to the point of almost being on a virtual machine, until it gives up that connection and somehow proves it hasn't been subverted. I'm a bit fuzzy on what evidence would fly with that court, but it would definitely be a 'guilty until proven innocent' lawbook in front of a hanging judge.
For individuals - Security Through Obscurity, and maybe just apathy. Out of the millions of people out there, what are the chances 'they' are cracking open and decrypting your packets in particular? Or even care about the fact that those are your packets? Or care about you?
For people who actually have things to hide that anyone tapping in may be interested in - not mentioning any information that would be relevant within an hour (the usual shortest decryption period for audio, but much shorter for text), but probably using burner devices. (Another reason to not get a smartphone in your head.)
What could a general society be like in this world, where any idiot 'hacker' with a radio antenna nearby might be seeing everything you text within a few hours, depending on his decryption software?
How would social media (both consumers using it and the companies providing it) look in that digital environment?
What alternate ideas are there to preserve security in such a world?
How would the the normal people within this setting be impacted? The ones not out there on motorcycles or bashing faces in with cybernetic arms. Maybe more "if you knew nothing you sent over the internet was secure for more than a couple hours, how would your life change?"
I'm not sure if the question is too broadly defined for here, but I'm looking mostly for ideas on "how would this look in 'civilian' life?"