Enforce the full OpenPGP fingerprint of ppa:bitcoin/bitcoin

Previously, basically anyone in the position to MITM the network
connection of the build server for this image could have easily
compromised it!

Source: https://launchpad.net/~bitcoin/+archive/ubuntu/bitcoin

Author: ypid

Dockerfile

@@ -14,7 +14,7 @@ ENV GROUP_ID ${GROUP_ID:-1000}
 RUN groupadd -g ${GROUP_ID} bitcoin \
 	&& useradd -u ${USER_ID} -g bitcoin -s /bin/bash -m -d /bitcoin bitcoin
 
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8842ce5e && \
+RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C70EF1F0305A1ADB9986DBD8D46F45428842CE5E && \
     echo "deb http://ppa.launchpad.net/bitcoin/bitcoin/ubuntu xenial main" > /etc/apt/sources.list.d/bitcoin.list
 
 RUN apt-get update && apt-get install -y --no-install-recommends \