document how to check how much entropy is avail on linux

diff --git a/src/RNGs.tex b/src/RNGs.tex
index dbfc825..0982327 100644 (file)
--- a/src/RNGs.tex
+++ b/src/RNGs.tex
@@ -50,6 +50,7 @@ time when entropy is low keeps this low-entropy situation for hours
 leading to predictable session keys~\cite{HDWH12}.
 
 \subsection{Linux}
+\label{subsec:RNG-linux}
 
 On Linux there are two devices that return random bytes when read, the
 \verb+/dev/random+ can block until sufficient entropy has been collected
@@ -67,6 +68,11 @@ file before shutdown and re-injecting the contents during the boot
 process. On the other hand this can be used for running a secondary
 entropy collector to inject entropy into the kernel entropy pool.
 
+On Linux you can check how much entropy is available with the command:
+\begin{lstlisting}
+$ cat /proc/sys/kernel/random/entropy_avail
+\end{lstlisting}
+
 %% specifics for libraries
 %% Openssl uses /dev/urandom. See the paper: https://factorable.net/weakkeys12.conference.pdf (section 5.2)
 %% What about other libs? 

diff --git a/src/practical_settings/GPG.tex b/src/practical_settings/GPG.tex
index b062f4c..1ab09ff 100644 (file)
--- a/src/practical_settings/GPG.tex
+++ b/src/practical_settings/GPG.tex
@@ -24,6 +24,8 @@ cert-digest-algo SHA256
 default-preference-list SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAST5 ZLIB BZIP2 ZIP Uncompressed
 \end{lstlisting}
 
+Before you generate a new PGP key, make sure there is enough entropy available (see subsection \ref{subsec:RNG-linux}).
+
 %\subsubsection{PGP / GPG Operations}
 
 %% Ciphering - Unciphering operations

diff --git a/src/theory/RNGs.tex b/src/theory/RNGs.tex
index 25f80c6..4cc18c9 100644 (file)
--- a/src/theory/RNGs.tex
+++ b/src/theory/RNGs.tex
@@ -59,6 +59,7 @@ time when entropy is low keeps this low-entropy situation for hours
 leading to predictable session keys~\cite{HDWH12}.
 
 \subsection{Linux}
+\label{subsec:RNG-linux}
 
 \todo{Other architectures, BSD, Windows?}
 
@@ -78,6 +79,11 @@ file before shutdown and re-injecting the contents during the boot
 process. On the other hand this can be used for running a secondary
 entropy collector to inject entropy into the kernel entropy pool.
 
+On Linux you can check how much entropy is available with the command:
+\begin{lstlisting}
+$ cat /proc/sys/kernel/random/entropy_avail
+\end{lstlisting}
+
 %% specifics for libraries
 %% Openssl uses /dev/urandom. See the paper: https://factorable.net/weakkeys12.conference.pdf (section 5.2)
 %% What about other libs?