Open Source Week 11

Open Source Computing

Week 11

The xz attack

A serious supply-chain attack on ssh was published on March 29, 2024, by Andres Freund, who discovered it by noting a minor timing mismatch in ssh.

See ../mnotes/security.html#xz

Cathedral v Bazaar

Criticisms of fetchmail

Discussion of how to explain what a calculator does

pressing the first digit, following an operation: save some things, clear the display, and put the new digit there
pressing another digit: put them into the display
pressing operator: clear the display, storing it in prev_display
pressing equals: combining prev_display and current display with the operator.

expression evaluation: ~/271/expressions (code should be in pld.cs.luc.edu/courses/271/spr18/demos/expressionsij.zip)

java expr_eval (traced version is expr_exp)

java expr_assign

Notes: pld.cs.luc.edu/courses/271/spr18/mnotes/recursion.html#exprtrees

Demo of command-line expressions

With a calculator interface, things are a little different. Generally, the '(' key clears the display and starts a new subexpression. Operator keys might display the current operator on the screen. The ')' key acts like the '=' key for the current expression, displaying the results so far. galculator takes this approach.

The other alternative is to display the entire expression on the display line. qalculate does this.