Home / ubuntu / Questions / 953971
Accepted
NerdOfLinux
Asked: 2017-09-09 07:17:08 +0800 CST

Why does displaying an encrypted string in the terminal or nano make weird symbols?

  • 772

I have an encrypted file that is encoded with base64:

U2FsdGVkX19hoS7DQSHERIkTzT3Hp7RUEjMAh6UDOP6YjRB/XQey7TKoySJiZTni
WbCfJLhihMD9CkohBnvrY8UBkh2dbi1K6hQqf8X9ENGFNWUxqmhYMG+WrBsPwhpB
I1qUt91IKlPS1YMZ0UDyBieDwFyqFi3izGhqXoOuzo8=

and when I run:

cat encryptedfile | openssl enc -d -a

I get a bunch of question mark symbols. Why does that happen?

encryption

2 Answers

  1. Best Answer

    Let's see what file has to say about your data:

    $ base64 -d <<EOF | file - 
U2FsdGVkX19hoS7DQSHERIkTzT3Hp7RUEjMAh6UDOP6YjRB/XQey7TKoySJiZTni
WbCfJLhihMD9CkohBnvrY8UBkh2dbi1K6hQqf8X9ENGFNWUxqmhYMG+WrBsPwhpB
I1qUt91IKlPS1YMZ0UDyBieDwFyqFi3izGhqXoOuzo8=
EOF
/dev/stdin: openssl enc'd data with salted password

    So, after base64-decoding, you get the encrypted data. And now with od -c:

    $ base64 -d <<EOF | od -c 
U2FsdGVkX19hoS7DQSHERIkTzT3Hp7RUEjMAh6UDOP6YjRB/XQey7TKoySJiZTni
WbCfJLhihMD9CkohBnvrY8UBkh2dbi1K6hQqf8X9ENGFNWUxqmhYMG+WrBsPwhpB
I1qUt91IKlPS1YMZ0UDyBieDwFyqFi3izGhqXoOuzo8=
EOF
0000000   S   a   l   t   e   d   _   _   a 241   . 303   A   ! 304   D
0000020 211 023 315   = 307 247 264   T 022   3  \0 207 245 003   8 376
0000040 230 215 020 177   ]  \a 262 355   2 250 311   "   b   e   9 342
0000060   Y 260 237   $ 270   b 204 300 375  \n   J   ! 006   { 353   c
0000100 305 001 222 035 235   n   -   J 352 024   * 177 305 375 020 321
0000120 205   5   e   1 252   h   X   0   o 226 254 033 017 302 032   A
0000140   #   Z 224 267 335   H   *   S 322 325 203 031 321   @ 362 006
0000160   ' 203 300   \ 252 026   - 342 314   h   j   ^ 203 256 316 217
0000200

    Clearly not all of those bytes are text in our usual encodings (ASCII or UTF-8). The terminal has no way to make sense of most of those bytes, and shows them as question marks. Some of those show up as ASCII text, some as symbols higher up in the Unicode chart (Ώ, for example), because the terminal tries to make some sense of the data.

    Encrypted data is not expected to be text, so there's no reason for it to stick byte sequences permitted by some encoding. It can use any sequence of bytes available, and it does.

    • 3

  2. A base64 encoded string consists only of 64 printable characters,
    e.g. for MIME base64 A-Z, a-z, 0-9, +, /.

    If you decode the string you will get the full byte range from 0..255 which also contains non-printable characters like control characters which show up as question marks.

    • 1