Tenure-track working career math

AbstractA knot is said to be slice if it bounds a smooth properly embedded disk in . We demonstrate that the Conway knot is not slice. This completes the classification of slice knots under 13 crossings and gives the first example of a non-slice knot which is both topologically slice and a positive mutant of […]

More on David’s numbering the people

David had a lot more numbering and statistics going on in the Bible than we alluded to earlier. https://www.mushroom.global/2020/04/16/davids-numbering-the-people-absaloms-haircut/ (8) Tu mets devant toi nos iniquités, Et à la lumière de ta face nos fautes cachées. (9) Tous nos jours disparaissent par ton courroux; Nous voyons nos années s’évanouir comme un son. (10) Les jours […]

Broken SHA hashes and cryptocurrency

https://arstechnica.com/information-technology/2020/01/pgp-keys-software-security-and-much-more-threatened-by-new-sha1-exploit/ https://www.schneier.com/blog/archives/2020/01/new_sha-1_attac.html https://www.tomshardware.com/news/researchers-reveal-new-sha-1-attack https://en.bitcoin.it/wiki/SHA-256 The SHA hash used in Bitcoin is iterated, or re-applied to its output. When a hash function is iterated for a second time in this manner, the size of its range is reduced by an approximate factor of by random collisions. The iterated hash function itself can also be iterated, and […]