Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p><sup>If your input buffer is not a multiplicity of a 16-byte block, you need to stuff the last block with dummy bytes. If the last block is less than 16 bytes it is dropped by crypto++ and not encrypted. When decrypting, you need to truncate the dummy bytes. That 'another way' you are referring to, already does the addition and truncation for you. So what should be the dummy bytes, to know how many of them there is, thus should be truncated? I use the following pattern: fill each byte with the value of dummies count.</sup></p> <p><sup>Examples: You need to add 8 bytes? set them to 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08. You need to add 3 bytes? set them to 0x03, 0x03, 0x03 etc.</sup></p> <p><sup>When decrypting, get the value of last byte of the output buffer. Assume it is N. Check, if the values last N bytes are equal to N. Truncate, if true.</sup></p> <p><strong>UPDATE:</strong></p> <pre><code>CryptStreamBuffer::CryptStreamBuffer(istream&amp; encryptedInput, CryptoPP::StreamTransformation&amp; c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c, 0, CryptoPP::BlockPaddingSchemeDef::ZEROS_PADDING); m_Source = new CryptoPP::FileSource(encryptedInput, false, m_StreamTransformationFilter); } CryptStreamBuffer::CryptStreamBuffer(ostream&amp; encryptedOutput, CryptoPP::StreamTransformation&amp; c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_Sink = new CryptoPP::FileSink(encryptedOutput); m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c, m_Sink, CryptoPP::BlockPaddingSchemeDef::ZEROS_PADDING); } </code></pre> <p>Setting the ZEROS_PADDING made your code working (tested on text files). However why it does not work with DEFAULT_PADDING - I did not find the cause yet.</p>
    singulars
    1. This table or related slice is empty.
    1. POCan anyone explain why my crypto++ decrypted file is 16 bytes short?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USAoi Karasu
    1. USAoi Karasu
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI do not believe this is the problem. With crypto++ the StreamTransformationFilter automatically stuffs the last block. That is what the call to MessageEnd() is for in sync(). Though I don't think sync() is ultimately the correct place for it.
      singulars
      1. PO
      1. USTom Williams
    2. CO`int CryptStreamBuffer::sync() { if (m_Sink) { m_StreamTransformationFilter->MessageEnd(); } }` Why there is no return value here? Does your code compile? I cannot compile it?
      singulars
      1. PO
      1. USAoi Karasu
    3. COUm. What if my file just so happens to end in the byte `0x01`? Prepend the data size to the data before padding if you need this kind of thing: for strong cryptography doing so won't provide a useful crib.
      singulars
      1. PO
      1. USSteve Jessop
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload