On extraction there is a difference on the output dependend if the archive has a encrypted header or not. Here is an example:
sworddragon@ubuntu:~/tmp$ echo 1 > test
sworddragon@ubuntu:~/tmp$ 7z a -p1 test1.7z7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
p7zip Version 9.20 (locale=de_DE.UTF-8,Utf16=on,HugeFiles=on,6 CPUs)
ScanningCreating archive test1.7z
Compressing test
Everything is Ok
sworddragon@ubuntu:~/tmp$ 7z a -mhe=on -p1 test2.7z7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
p7zip Version 9.20 (locale=de_DE.UTF-8,Utf16=on,HugeFiles=on,6 CPUs)
ScanningCreating archive test2.7z
Compressing test
Compressing test1.7zEverything is Ok
sworddragon@ubuntu:~/tmp$ 7z x test1.7z7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
p7zip Version 9.20 (locale=de_DE.UTF-8,Utf16=on,HugeFiles=on,6 CPUs)Processing archive: test1.7z
Enter password (will not be echoed) :
file test
already exists. Overwrite with
test?
(Y)es / (N)o / (A)lways / (S)kip all / A(u)to rename all / (Q)uit? qBreak signaled
sworddragon@ubuntu:~/tmp$ 7z x test2.7z7-Zip [64] 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
p7zip Version 9.20 (locale=de_DE.UTF-8,Utf16=on,HugeFiles=on,6 CPUs)Processing archive: test2.7z
Enter password (will not be echoed) :
Error: Can not open encrypted archive. Wrong password?
Without archive header encryption between "Processing archive: *" and "Enter password (will not be echoed) :" there are 2 empty lines but with header encryption there is only 1 empty line.