SlunkCrypt

An experimental cryptography library and command-line tool.

Legal Warning

Use of SlunkCrypt may be illegal in countries where encryption is outlawed. We believe it is legal to use SlunkCrypt in many countries all around the world, but we are not lawyers, and so if in doubt you should seek legal advice before downloading it. You may find useful information at cryptolaw.org, which collects information on cryptography laws in many countries, but we can't vouch for its correctness.

Command-line Usage

This section describes the SlunkCypt command-line program:

Synopsis:

slunkcrypt --encrypt [[@][:]<passphrase>] <input.txt> <output.enc>
slunkcrypt --decrypt [[@][:]<passphrase>] <input.enc> <output.txt>

Commands:

• --encrypt (-e):
  Encrypt the plaintext in the given input file. The ciphertext is written to the specified output file.
• --decrypt (-d):
  Decrypt the ciphertext in the given input file. The plaintext is written to the specified output file.
• --self-test (-t):
  Run self-test and exit application.

Options:

• If <passphrase> is prefixed with a @ character, then it specifies the file to read the passphrase from.
  Note: Only the first non-empty line in the specified file is used!
• If <passphrase> is prefixed with a : character, then the leading character is ignored.
• If <passphrase> is omitted, then the passphrase is read from the SLUNK_PASSPHRASE environment variable.
• If <passphrase> is set to @-, then the passphrase is read from the standard input stream.

Programming Interface (API)

C99 API

This section describes the "low-level" C99 API of the SlunkCypt library:

slunkcrypt_alloc()

Allocate and initialize a new SlunkCrypt encryption/decryption context.

slunkcrypt_t slunkcrypt_alloc(
    const uint64_t nonce,
    const uint8_t *const passwd,
    const size_t passwd_len
);

Parameters:

• nonce
  The nonce (number used once) to be used for the encryption/decryption process. The purpose of the nonce is to ensure that each message will be encrypted differently, even when the same password is used to encrypt multiple (possibly identical) messages. Therefore, a new random nonce must be chosen for each message to be encrypted! It is not necessary to keep the nonce confidential, but the same nonce must be used for both, encryption and decryption. Typically, the nonce is stored/transmitted alongside the ciphertext.

  Note: It is recommended to generate a random nonce via the slunkcrypt_generate_nonce() function for each message!

• passwd
  The password to "protect" the message. The password is given as an array of bytes (e.g. UTF-8 encoded characters) of type uint8_t; a terminating NULL character is not required, as the length of the password is specified explicitly. The same password may be used to encrypt multiple messages. Also, the same password must be used for both, encryption and decryption; it will only be possible decrypt the ciphertext, if the "correct" password is known. The password must be kept confidential under all circumstances!

  Note: In order to thwart brute force attacks, it is recommended to choose a "random" password that is at least 12 characters in length and that consists of upper-case characters, lower-case characters, digits as well as other "special" characters.

• passwd_len
  The length of password given by the passwd parameter, in bytes, not counting a terminating NULL character. The minimum/maximum length of the password are given by the SLUNKCRYPT_PWDLEN_MIN and SLUNKCRYPT_PWDLEN_MAX constants, respectively.

Return value:

• If successful, a handle to the new SlunkCrypt context is return; otherwise SLUNKCRYPT_NULL is returned.

  Note: Applications should treat slunkcrypt_t as an opaque handle type. Also, as soon as the SlunkCrypt context is not needed anymore, the application shall call slunkcrypt_free() in order to "clear" and de-allocate that context.

slunkcrypt_reset()

Re-initialize an existing SlunkCrypt encryption/decryption context.

int slunkcrypt_reset(
    const slunkcrypt_t context,
    const uint64_t nonce,
    const uint8_t *const passwd,
    const size_t passwd_len
);

Parameters:

• context
  The existing SlunkCrypt context to be re-initialized. This must be a valid handle that was returned by a previous invocation of the slunkcrypt_alloc() function and that has not been free'd since then.

• nonce
  Please refer to the slunkcrypt_alloc() function for details!

• passwd
  Please refer to the slunkcrypt_alloc() function for details!

• passwd_len
  Please refer to the slunkcrypt_alloc() function for details!

Return value:

• If successful, SLUNKCRYPT_SUCCESS is returned; otherwise SLUNKCRYPT_FAILURE or SLUNKCRYPT_ABORTED is returned.

slunkcrypt_free()

De-allocate an existing SlunkCrypt encryption/decryption context. This will "clear" and release any memory occupied by the context.

void slunkcrypt_free(
    const slunkcrypt_t context
);

Parameters:

• context
  The existing SlunkCrypt context to be de-allocated. This must be a valid handle that was returned by a previous invocation of the slunkcrypt_alloc() function and that has not been free'd since then.

  Note: Once a handle has been passed to this function, that handle is invalidated and must not be used again!

slunkcrypt_generate_nonce()

Generate a new random nonce (number used once), using the system's "cryptographically secure" entropy source.

int slunkcrypt_generate_nonce(
  int64_t* const nonce
);

Parameters:

• nonce
  A pointer to a variable of type int64_t that receives the new random nonce.

Return value:

• If successful, SLUNKCRYPT_SUCCESS is returned; otherwise SLUNKCRYPT_FAILURE or SLUNKCRYPT_ABORTED is returned.

License

This work has been released under the CC0 1.0 Universal license.

For details, please refer to:
https://creativecommons.org/publicdomain/zero/1.0/legalcode