Physical Danger
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For Gareth Williams, the MI6 "spy-in-a-bag," the combination of math skills and the Secret Intelligence Service didn't work out so well.
For nearly every other real-life cryptographer, the field has been physically safe beyond the usual desk-job-related health issues: carpal tunnel, misaligned hips (for real), something called Computer Vision Syndrome (for real, for real), and so on.
Buy an ergonomic chair, drag your butt to 7:00AM yoga classes, and you'll be fine.