Class: Omnizip::Formats::Rar::Rar5::Encryption::KeyDerivation

Inherits:
Object
  • Object
show all
Defined in:
lib/omnizip/formats/rar/rar5/encryption/key_derivation.rb

Overview

RAR5 password-based key derivation

RAR5 uses PBKDF2-HMAC-SHA256 for key derivation, which is more secure than 7-Zip's iterative SHA-256 approach.

The process:

  1. Generate random salt (16 bytes)
  2. Apply PBKDF2-HMAC-SHA256 with configurable iterations
  3. Derive 32-byte AES-256 key

Examples:

Derive key from password

salt = SecureRandom.random_bytes(16)
key = KeyDerivation.derive_key("password", salt, 262_144)

Constant Summary collapse

DEFAULT_ITERATIONS =

Default PBKDF2 iterations (262,144 = 2^18) This provides good security while maintaining reasonable performance

262_144
MIN_ITERATIONS =

Minimum iterations (2^16 = 65,536)

65_536
MAX_ITERATIONS =

Maximum iterations (2^20 = 1,048,576)

1_048_576
SALT_SIZE =

Salt size (16 bytes)

16
KEY_SIZE =

Key size (32 bytes for AES-256)

32

Class Method Summary collapse

Class Method Details

.derive_key(password, salt, iterations = DEFAULT_ITERATIONS) ⇒ String

Derive AES-256 key from password using PBKDF2-HMAC-SHA256

Parameters:

  • password (String) —

    User password

  • salt (String) —

    Random salt (16 bytes)

  • iterations (Integer) (defaults to: DEFAULT_ITERATIONS) —

    Number of PBKDF2 iterations

Returns:

  • (String) —

    32-byte AES-256 key

Raises:

  • (ArgumentError) —

    If password empty or salt wrong size



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# File 'lib/omnizip/formats/rar/rar5/encryption/key_derivation.rb', line 48

def self.derive_key(password, salt, iterations = DEFAULT_ITERATIONS)
  validate_inputs(password, salt, iterations)

  # PBKDF2-HMAC-SHA256
  OpenSSL::PKCS5.pbkdf2_hmac(
    password,
    salt,
    iterations,
    KEY_SIZE,
    OpenSSL::Digest.new("SHA256"),
  )
end

.generate_salt ⇒ String

Generate random salt

Returns:

  • (String) —

    16-byte random salt



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# File 'lib/omnizip/formats/rar/rar5/encryption/key_derivation.rb', line 64

def self.generate_salt
  SecureRandom.random_bytes(SALT_SIZE)
end