Improved (AMS) blackboard math font.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -27,7 +27,7 @@
 \RequirePackage{lmodern}
 \RequirePackage{bold-extra}
 \RequirePackage{quattrocento}
-\RequirePackage{dsfont}
+\RequirePackage[bb=ams]{mathalfa}
 
 % Quattrocento is beautiful but doesn't have an italic face. So we scale
 % New Century Schoolbook italic to fit in with slanted Quattrocento and
@@ -337,7 +337,7 @@ electronic commerce and payment, financial privacy, proof of work, zero knowledg
 % conventions
 \newcommand{\bytes}[1]{\underline{\raisebox{-0.22ex}{}\smash{#1}}}
 \newcommand{\zeros}[1]{[0]^{#1}}
-\newcommand{\bit}{\mathds{B}}
+\newcommand{\bit}{\mathbb{B}}
 \newcommand{\Nat}{\mathbb{N}}
 \newcommand{\PosInt}{\mathbb{N}^+}
 \newcommand{\Rat}{\mathbb{Q}}