Include the b2sum for the original data in the generated PDF file.

This aids in verification
 1) after creation, that a PDF was created which can be successfully
    restored --> see new paperbackup-verify.sh script
 2) after restoration, by running b2sum on the restored data, that the
    restoration has indeed produced the exact same data as had been
    in the original file

Author: tuxlifan

paperbackup-verify.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/bash
+
+# USAGE: paperbackup-verify.sh backup.pdf
+#   where backup.pdf should be the pdf created with paperbackup.py
+
+RESTOREPROG=$(dirname $0)/paperrestore.sh
+
+rPDF=$( $RESTOREPROG $1 )
+
+bPDF=$(echo "$rPDF" | b2sum | cut -d ' ' -f 1 )
+bEmbedded=$(pdftotext $1 - | grep b2sum -A2 | tail -2 | tr -d '\n')
+
+if [ "x$bPDF" == "x$bEmbedded" ]; then
+    echo "b2sums MATCH :-)"
+    echo
+    exit 0
+else
+    echo "Creating diff:"
+    echo "$rPDF" | diff ${1%.*} -
+    diffret=$?
+    echo
+    if [ $diffret -ne 0 ]; then
+        echo "diff and b2sums do NOT match!"
+        echo "restored b2sum from PDF: " $bPDF
+        echo "original b2sum embedded: " $bEmbedded
+        echo
+        exit 11
+    else
+        echo "diff matches but b2sum is missing."
+        echo
+        exit 1
+    fi
+fi

paperbackup.py

@@ -35,6 +35,7 @@
 import qrencode
 from tempfile import mkstemp
 from datetime import datetime
+from shutil import which
 from PIL import Image
 from pyx import *
 
@@ -171,6 +172,9 @@ def finish_page(pdf, canv, pageno):
 
     chksumlines.append(line)
 
+# we also want a checksum which the restored file should match
+b2sum = hashlib.blake2b(bytes(ascdata, 'utf8')).hexdigest()
+
 # add some documentation around the plaintest
 outlines=[]
 coldoc=" "*splitat
@@ -179,6 +183,10 @@ def finish_page(pdf, canv, pageno):
 outlines.extend(chksumlines)
 outlines.append("")
 outlines.append("")
+outlines.append("b2sum of input file (split over 2 lines):")
+outlines.append("%s"%b2sum[:64])
+outlines.append("%s"%b2sum[64:])
+outlines.append("")
 outlines.append("")
 outlines.append("--")
 outlines.append("Created with paperbackup.py")
@@ -216,3 +224,16 @@ def finish_page(pdf, canv, pageno):
 
 os.remove(temp_text_path)
 os.remove(temp_barcode_path)
+
+verify_prog = which("paperbackup-verify.sh")
+if not verify_prog:
+    verify_prog = which("paperbackup-verify")
+if not verify_prog:
+    verify_prog = which(os.path.join(os.path.dirname(sys.argv[0]), "paperbackup-verify.sh"))
+if not verify_prog:
+    print("\n  NOTE:  Could not find 'paperbackup-verify' program which should have been")
+    print(  "           installed together with {}! ".format(sys.argv[0]))
+    verify_prog = "paperbackup-verify"
+print("\n  !!!!!!!!!")
+print("  ATTENTION:  Running '{} {}.pdf' NOW is STRONGLY advised to".format(verify_prog, just_filename))
+print("  !!!!!!!!!     verify that zbarimg can read back the generated qr codes!\n")