:~$ echo "Hello world! How are you today?" | openssl des-cbc -e -k mypass -S 0 -out enc.bin :~$ openssl des-cbc -d -k mypass -in enc.bin Hello world! How are you today? :~$ hexedit enc.bin # at 0x10 we change B6 to B7, i.e. we flip the first message bit ~$ openssl des-cbc -d -k mypass -in enc.bin Z?��6���sld! How are you today? :~$ echo "Hello world! How are you today?" | openssl des-ofb -e -k mypass -S 0 -out enc.bin :~$ openssl des-ofb -d -k mypass -in enc.bin Hello world! How are you today? :~$ hexedit enc.bin # at 0x10 we change 9A to 9B, i.e. we flip the first message bit :~$ openssl des-ofb -d -k mypass -in enc.bin Iello world! How are you today?