I'm creating an RSA key pair in Bouncy Castle and need to specify an int value for certainty. This Stack Overflow answer says it is a relative test for how prime the values are.
There is another answer that says this value should be adjusted relative to the key length.
Question
What are the correct values for certainty relative to key length (how did you determine this?)
What does it mean to say "certainty of x bits" of a number? (If it's possible to sub-divide a number and certify bits, which bits are being certified?)