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1.1 |
=head1 NAME |
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Crypt::Spritz - Spritz stream cipher/hash/MAC/AEAD/CSPRNG family |
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=head1 SYNOPSIS |
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use Crypt::Spritz; |
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1.5 |
# see the commented examples in their respective classes, |
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# but basically |
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my $cipher = new Crypt::Spritz::Cipher::XOR $key, $iv; |
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$ciphertext = $cipher->crypt ($cleartext); |
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1.1 |
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my $hasher = new Crypt::Spritz::Hash; |
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$hasher->add ($data); |
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$digest = $hasher->finish; |
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my $hasher = new Crypt::Spritz::MAC $key; |
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$hasher->add ($data); |
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$mac = $hasher->finish; |
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my $aead = new Crypt::Spritz::AEAD::XOR $key; |
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$aead->nonce ($counter); |
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$aead->associated_data ($header); |
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$ciphertext = $aead->crypt ($cleartext); |
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$mac = $aead->mac; |
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my $prng = new Crypt::Spritz::PRNG $entropy; |
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$prng->add ($additional_entropy); |
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$keydata = $prng->get (32); |
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=head1 DESCRIPTION |
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This module implements the Spritz spongelike function (with N=256), the |
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spiritual successor of RC4 developed by Ron Rivest and Jacob Schuldt. |
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1.4 |
Its strength is extreme versatility (you get a stream cipher, a hash, a |
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MAC, a DRBG/CSPRNG, an authenticated encryption block/stream cipher and |
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more) and extremely simple and small code (encryption and authentication |
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can be had in 1KB of compiled code on amd64, which isn't an issue for most |
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uses in Perl, but is useful in embedded situations, or e.g. when doing |
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crypto using javascript in a browser and communicating with Perl). |
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Its weakness is its relatively slow speed (encryption is a few times |
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slower than RC4 or AES, hashing many times slower than SHA-3, although |
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this might be reversed on an 8-bit-cpu) and the fact that it is totally |
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unproven in the field (as of this writing, the cipher was just a few |
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months old), so it can't be called production-ready. |
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All the usual caveats regarding stream ciphers apply - never repeat your |
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key, never repeat your nonce and so on - you should have some basic |
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understanding of cryptography before using this cipher in your own |
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designs. |
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The Spritz base class is not meant for end users. To make usage simpler |
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and safer, a number of convenience classes are provided for typical |
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end-user tasks: |
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encryption - Crypt::Spritz::Cipher::XOR |
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hashing - Crypt::Spritz::Hash |
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message authentication - Crypt::Spritz::MAC |
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authenticated encryption - Crypt::Spritz::AEAD::XOR |
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random number generation - Crypt::Spritz::PRNG |
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=cut |
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package Crypt::Spritz; |
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use XSLoader; |
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$VERSION = '0.1'; |
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XSLoader::load __PACKAGE__, $VERSION; |
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@Crypt::Spritz::ISA = Crypt::Spritz::Base::; |
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1.2 |
@Crypt::Spritz::Hash::ISA = |
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@Crypt::Spritz::PRNG::ISA = |
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@Crypt::Spritz::Cipher::ISA = |
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@Crypt::Spritz::AEAD::ISA = Crypt::Spritz::Base::; |
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@Crypt::Spritz::MAC::ISA = Crypt::Spritz::Hash::; |
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@Crypt::Spritz::Cipher::XOR::ISA = Crypt::Spritz::Cipher::; |
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@Crypt::Spritz::AEAD::XOR::ISA = Crypt::Spritz::AEAD::; |
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sub Crypt::Spritz::Cipher::keysize () { 32 } |
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sub Crypt::Spritz::Cipher::blocksize () { 64 } |
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*Crypt::Spritz::Hash::new = \&Crypt::Spritz::new; |
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*Crypt::Spritz::Hash::add = |
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*Crypt::Spritz::PRNG::add = \&Crypt::Spritz::absorb; |
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*Crypt::Spritz::PRNG::get = \&Crypt::Spritz::squeeze; |
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*Crypt::Spritz::AEAD::new = \&Crypt::Spritz::MAC::new; |
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*Crypt::Spritz::AEAD::finish = \&Crypt::Spritz::Hash::finish; |
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*Crypt::Spritz::AEAD::associated_data = |
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*Crypt::Spritz::AEAD::nonce = \&Crypt::Spritz::absorb_and_stop; |
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=head2 THE Crypt::Spritz CLASS |
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This class implements most of the Spritz primitives. To use it effectively |
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you should understand them, for example, by reading the L<Spritz |
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paper/http://people.csail.mit.edu/rivest/pubs/RS14.pdf>, especially |
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pp. 5-6. |
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The Spritz primitive corresponding to the Perl method is given as |
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comment. |
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=over 4 |
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=item $spritz = new Crypt::Spritz # InitializeState |
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Creates and returns a new, initialised Spritz state. |
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=item $spritz->init # InitializeState |
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Initialises the Spritz state again, throwing away the previous state. |
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=item $another_spritz = $spritz->clone |
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Make an exact copy of the spritz state. This method can be called on all |
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of the objects in this module, but is documented separately to give some |
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cool usage examples. |
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=item $spritz->update # Update |
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=item $spritz->whip ($r) # Whip |
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=item $spritz->crush # Crush |
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=item $spritz->shuffle # Shuffle |
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=item $spritz->output # Output |
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Calls the Spritz primitive ovf the same name - these are not normally |
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called manually. |
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=item $spritz->absorb ($I) # Absorb |
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1.6 |
Absorbs the given data into the state (usually used for key material, |
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nonces, IVs messages to be hashed and so on). |
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=item $spritz->absorb_stop # AbsorbStop |
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Absorbs a special stop symbol - this is usually used as delimiter between |
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multiple strings to be absorbed, to thwart extension attacks. |
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=item $spritz->absorb_and_stop ($I) |
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This is a convenience function that simply calls C<absorb> followed by |
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C<absorb_stop>. |
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=item $octet = $spritz->drip # Drip |
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Squeezes out a single byte from the state. |
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=item $octets = $spritz->squeeze ($len) # Squeeze |
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Squeezes out the requested number of bytes from the state - this is usually |
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=back |
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=head2 THE Crypt::Spritz::Cipher::XOR CLASS |
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This class implements stream encryption/decryption. It doesn't implement |
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the standard Spritz encryption but the XOR variant (called B<spritz-xor> |
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in the paper). |
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The XOR variant should be as secure as the standard variant, but |
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doesn't have separate encryption and decryaption functions, which saves |
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codesize. IT is not compatible with standard Spritz encryption, however - |
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drop me a note if you want that implemented as well. |
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Typical use for encryption I<and> decryption (code is identical for |
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decryption, you simply pass the encrypted data to C<crypt>): |
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# create a cipher - $salt can be a random string you send |
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# with your message, in clear, a counter (best), or empty if |
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# you only want to encrypt one message with the given key. |
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# 16 or 32 octets are typical sizes for the key, for the salt, |
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# use whatever you need to give a unique salt for every |
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# message you encrypt with the same key. |
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my $cipher = Crypt::Spritz::Cipher::XOR $key, $salt; |
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# encrypt a message in one or more calls to crypt |
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my $encrypted; |
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$encrypted .= $cipher->crypt ("This is"); |
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$encrypted .= $cipher->crypt ("all very"); |
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$encrypted .= $cipher->crypt ("secret"); |
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# that's all |
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=over 4 |
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=item $cipher = new Crypt::Spritz::Cipher::XOR $key[, $iv] |
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Creates a new cipher object usable for encryption and decryption. The |
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C<$key> must be provided, the initial vector C<$IV> is optional. |
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Both C<$key> and C<$IV> can be of any length. Typical lengths for the |
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C<$key> are 16 (128 bit) or 32 (256 bit), while the C<$IV> simply needs to |
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be long enough to distinguish repeated uses of tghe same key. |
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=item $encrypted = $cipher->crypt ($cleartext) |
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=item $cleartext = $cipher->crypt ($encrypted) |
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1.6 |
Encrypt or decrypt a piece of a message. This can be called as many times |
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1.4 |
as you want, and the message can be split into as few or many pieces as |
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required without affecting the results. |
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=item $cipher->crypt_inplace ($cleartext_or_ciphertext) |
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Same as C<crypt>, except it I<modifies the argument in-place>. |
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1.6 |
=item $another_cipher = $cipher->clone |
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Make an exact copy of the cipher state. This can be useful to cache states |
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for reuse later, for example, to avoid expensive key setups. |
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While there might be use cases for this feature, it makes a lot more sense |
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for C<Crypt::Spritz::AEAD> and C<Crypt::Spritz::AEAD::XOR>, as they allow |
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you to specify the IV/nonce separately. |
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1.4 |
=item $constant_32 = $cipher->keysize |
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=item $constant_64 = $cipher->blocksize |
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These methods are provided for L<Crypt::CBC> compatibility and simply |
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return C<32> and C<64>, respectively. |
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Note that it is pointless to use Spritz with L<Crypt::CBC>, as Spritz is |
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not a block cipher and already provides an appropriate mode. |
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1.3 |
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1.4 |
=back |
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=head2 THE Crypt::Spritz::Hash CLASS |
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This implements the Spritz digest/hash algorithm. It works very similar to |
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other digest modules on CPAN, such as L<Digest::SHA3>. |
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Typical use for hashing: |
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# create hasher object |
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my $hasher = new Crypt::Spritz::Hash; |
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# now feed data to be hashed into $hasher |
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# in as few or many calls as required |
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$hasher->add ("Some data"); |
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$hasher->add ("Some more"); |
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# extract the hash - the object is not usable afterwards |
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my $digest = $hasher->finish (32); |
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=over 4 |
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=item $hasher = new Crypt::Spritz::Hash |
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Creates a new hasher object. |
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=item $hasher->add ($data) |
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Adds data to be hashed into the hasher state. It doesn't matter whether |
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you pass your data in in one go or split it up, the hash will be the same. |
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=item $digest = $hasher->finish ($length) |
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Calculates a hash digest of the given length and return it. The object |
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cannot sensibly be used for further hashing afterwards. |
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Typical digest lengths are 16 and 32, corresponding to 128 and 256 bit |
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digests, respectively. |
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1.6 |
=item $another_hasher = $hasher->clone |
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Make an exact copy of the hasher state. This can be useful to generate |
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incremental hashes, for example. |
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Example: generate a hash for the data already fed into the hasher, by keeping |
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the original hasher for further C<add> calls and calling C<finish> on a C<clone>. |
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my $intermediate_hash = $hasher->clone->finish; |
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Example: hash 64KiB of data, and generate a hash after every kilobyte that |
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is over the full data. |
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my $hasher = new Crypt::Spritz::Hash; |
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for (0..63) { |
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my $kib = "x" x 1024; # whatever data |
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$hasher->add ($kib); |
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my $intermediate_hash = $hasher->clone->finish; |
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... |
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} |
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These kind of intermediate hashes are sometimes used in communications |
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protocols to protect the integrity of the data incrementally, e.g. to |
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detect errors early, while still having a complete hash at the end of a |
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transfer. |
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1.4 |
=back |
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=head2 THE Crypt::Spritz::MAC CLASS |
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This implements the Spritz Message Authentication Code algorithm. It works |
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very similar to other digest modules on CPAN, such as L<Digest::SHA3>, but |
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implements an authenticated digest (like L<Digest::HMAC>). |
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I<Authenticated> means that, unlike L<Crypt::Spritz::Hash>, where |
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everybody can verify and recreate the hash value for some data, with a |
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MAC, knowledge of the (hopefully) secret key is required both to create |
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and to verify the digest. |
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Typical use for hashing is almost the same as with L<Crypt::Spritz::MAC>, |
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except a key (typically 16 or 32 octets) is provided to the constructor: |
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# create hasher object |
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my $hasher = new Crypt::Spritz::Mac $key; |
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# now feed data to be hashed into $hasher |
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# in as few or many calls as required |
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$hasher->add ("Some data"); |
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$hasher->add ("Some more"); |
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# extract the mac - the object is not usable afterwards |
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my $mac = $hasher->finish (32); |
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=over 4 |
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=item $hasher = new Crypt::Spritz::MAC $key |
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Creates a new hasher object. The C<$key> can be of any length, but 16 and |
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32 (128 and 256 bit) are customary. |
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=item $hasher->add ($data) |
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Adds data to be hashed into the hasher state. It doesn't matter whether |
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you pass your data in in one go or split it up, the hash will be the same. |
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=item $mac = $hasher->finish ($length) |
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1.1 |
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1.4 |
Calculates a message code of the given length and return it. The object |
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cannot sensibly be used for further hashing afterwards. |
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1.1 |
|
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1.4 |
Typical digest lengths are 16 and 32, corresponding to 128 and 256 bit |
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digests, respectively. |
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1.1 |
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1.6 |
=item $another_hasher = $hasher->clone |
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Make an exact copy of the hasher state. This can be useful to |
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generate incremental macs, for example. |
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See the description for the C<Crypt::Spritz::Hash::clone> method for some |
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examples. |
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1.4 |
=back |
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=head2 THE Crypt::Spritz::AEAD::XOR CLASS |
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This is the most complicated class - it combines encryption and |
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message authentication into a single "authenticated encryption |
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mode". It is similar to using both L<Crypt::Spritz::Cipher::XOR> and |
378 |
|
|
L<Crypt::Spritz::MAC>, but makes it harder to make mistakes in combining |
379 |
|
|
them. |
380 |
|
|
|
381 |
|
|
You can additionally provide cleartext data that will not be encrypted or |
382 |
|
|
decrypted, but that is nevertheless authenticated using the MAC, which |
383 |
|
|
is why this mode is called I<AEAD>, I<Authenticated Encryption with |
384 |
|
|
Associated Data>. Associated data is usually used to any header data that |
385 |
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|
is in cleartext, but should nevertheless be authenticated. |
386 |
|
|
|
387 |
|
|
This implementation implements the XOR variant. Just as with |
388 |
|
|
L<Crypt::Spritz::Cipher::XOR>, this means it is not compatible with |
389 |
|
|
the standard mode, but uses less code and doesn't distinguish between |
390 |
|
|
encryption and decryption. |
391 |
|
|
|
392 |
|
|
Typical usage is as follows: |
393 |
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|
|
394 |
|
|
# create a new aead object |
395 |
|
|
# you use one object per message |
396 |
|
|
# key length customarily is 16 or 32 |
397 |
|
|
my $aead = new Crypt::Spritz::AEAD::XOR $key; |
398 |
|
|
|
399 |
|
|
# now you must feed the nonce. if you do not need a nonce, |
400 |
|
|
# you can provide the empty string, but you have to call it |
401 |
|
|
# after creating the object, before calling associated_data. |
402 |
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|
# the nonce must be different for each usage of the $key. |
403 |
|
|
# a counter of some kind is good enough. |
404 |
|
|
# reusing a nonce with the same key completely |
405 |
|
|
# destroys security! |
406 |
|
|
$aead->nonce ($counter); |
407 |
|
|
|
408 |
|
|
# then you must feed any associated data you have. if you |
409 |
|
|
# do not have associated cleartext data, you can provide the empty |
410 |
|
|
# string, but you have to call it after nonce and before crypt. |
411 |
|
|
$aead->associated_data ($header); |
412 |
|
|
|
413 |
|
|
# next, you call crypt one or more times with your data |
414 |
|
|
# to be encrypted (opr decrypted). |
415 |
|
|
# all except the last call must use a length that is a |
416 |
|
|
# multiple of 64. |
417 |
|
|
# the last block can have any length. |
418 |
|
|
my $encrypted; |
419 |
|
|
|
420 |
|
|
$encrypted .= $aead->crypt ("1" x 64); |
421 |
|
|
$encrypted .= $aead->crypt ("2" x 64); |
422 |
|
|
$encrypted .= $aead->crypt ("3456"); |
423 |
|
|
|
424 |
|
|
# finally you can calculate the MAC for all of the above |
425 |
|
|
my $mac = $aead->finish; |
426 |
|
|
|
427 |
|
|
=over 4 |
428 |
|
|
|
429 |
|
|
=item $aead = new Crypt::Spritz::AEAD::XOR $key |
430 |
|
|
|
431 |
|
|
Creates a new cipher object usable for encryption and decryption. |
432 |
|
|
|
433 |
|
|
The C<$key> can be of any length. Typical lengths for the C<$key> are 16 |
434 |
|
|
(128 bit) or 32 (256 bit). |
435 |
|
|
|
436 |
|
|
After creation, you have to call C<nonce> next. |
437 |
|
|
|
438 |
|
|
=item $aead->nonce ($nonce) |
439 |
|
|
|
440 |
|
|
Provide the nonce value (nonce means "value used once"), a value the is |
441 |
|
|
unique between all uses with the same key. This method I<must> be called |
442 |
|
|
I<after> C<new> and I<before> C<associated_data>. |
443 |
|
|
|
444 |
|
|
If you only ever use a given key once, you can provide an empty nonce - |
445 |
|
|
but you still have to call the method. |
446 |
|
|
|
447 |
|
|
Common strategies to provide a nonce are to implement a persistent counter |
448 |
|
|
or to generate a random string of sufficient length to guarantee that it |
449 |
|
|
differs each time. |
450 |
root |
1.1 |
|
451 |
root |
1.4 |
The problem with counters is that you might get confused and forget |
452 |
|
|
increments, and thus reuse the same sequence number. The problem with |
453 |
|
|
random strings i that your random number generator might be hosed and |
454 |
|
|
generate the same randomness multiple times (randomness can be very hard |
455 |
|
|
to get especially on embedded devices). |
456 |
root |
1.1 |
|
457 |
root |
1.6 |
=item $aead->associated_data ($data) |
458 |
root |
1.1 |
|
459 |
root |
1.4 |
Provide the associated data (cleartext data to be authenticated but not |
460 |
|
|
encrypted). This method I<must> be called I<after> C<nonce> and I<before> |
461 |
|
|
C<crypt>. |
462 |
root |
1.1 |
|
463 |
root |
1.4 |
If you don't have any associated data, you can provide an empty string - |
464 |
|
|
but you still have to call the method. |
465 |
root |
1.1 |
|
466 |
root |
1.4 |
Associated data is typically header data - data anybody is allowed to |
467 |
|
|
see in cleartext, but that should nevertheless be protected with an |
468 |
|
|
authentication code. Typically such data is used to identify where to |
469 |
|
|
forward a message to, how to find the key to decrypt the message or in |
470 |
|
|
general how to interpret the encrypted part of a message. |
471 |
root |
1.1 |
|
472 |
root |
1.4 |
=item $encrypted = $cipher->crypt ($cleartext) |
473 |
root |
1.1 |
|
474 |
root |
1.4 |
=item $cleartext = $cipher->crypt ($encrypted) |
475 |
root |
1.1 |
|
476 |
root |
1.6 |
Encrypt or decrypt a piece of a message. This can be called as many times |
477 |
root |
1.4 |
as you want, and the message can be split into as few or many pieces as |
478 |
|
|
required without affecting the results, with one exception: All except the |
479 |
|
|
last call to C<crypt> needs to pass in a multiple of C<64> octets. The |
480 |
|
|
last call to C<crypt> does not have this limitation. |
481 |
root |
1.1 |
|
482 |
root |
1.4 |
=item $cipher->crypt_inplace ($cleartext_or_ciphertext) |
483 |
root |
1.1 |
|
484 |
root |
1.4 |
Same as C<crypt>, except it I<modifies the argument in-place>. |
485 |
root |
1.1 |
|
486 |
root |
1.6 |
=item $another_cipher = $cipher->clone |
487 |
|
|
|
488 |
|
|
Make an exact copy of the cipher state. This can be useful to cache states |
489 |
|
|
for reuse later, for example, to avoid expensive key setups. |
490 |
|
|
|
491 |
|
|
Example: set up a cipher state with a key, then clone and use it to |
492 |
|
|
encrypt messages with different nonces. |
493 |
|
|
|
494 |
|
|
my $cipher = new Crypt::Spritz::AEAD::XOR $key; |
495 |
|
|
|
496 |
|
|
my $message_counter; |
497 |
|
|
|
498 |
|
|
for my $message ("a", "b", "c") { |
499 |
|
|
my $clone = $cipher->clone; |
500 |
|
|
$clone->nonce (pack "N", ++$message_counter); |
501 |
|
|
$clone->associated_data (""); |
502 |
|
|
my $encrypted = $clone->crypt ($message); |
503 |
|
|
... |
504 |
|
|
} |
505 |
|
|
|
506 |
root |
1.4 |
=back |
507 |
|
|
|
508 |
|
|
|
509 |
|
|
=head2 THE Crypt::Spritz::PRNG CLASS |
510 |
|
|
|
511 |
|
|
This class implements a Pseudorandom Number Generatore (B<PRNG>), |
512 |
|
|
sometimes also called a Deterministic Random Bit Generator (B<DRBG>). In |
513 |
|
|
fact, it is even cryptographically secure, making it a B<CSPRNG>. |
514 |
|
|
|
515 |
|
|
Typical usage as a random number generator involves creating a PRNG |
516 |
|
|
object with a seed of your choice, and then fetching randomness via |
517 |
|
|
C<get>: |
518 |
|
|
|
519 |
|
|
# create a PRNG object, use a seed string of your choice |
520 |
|
|
my $prng = new Crypt::Spritz::PRNG $seed; |
521 |
|
|
|
522 |
|
|
# now call get as many times as you wish to get binary randomness |
523 |
|
|
my $some_randomness = $prng->get (17); |
524 |
|
|
my moree_randomness = $prng->get (5000); |
525 |
|
|
... |
526 |
|
|
|
527 |
|
|
Typical usage as a cryptographically secure random number generator is to |
528 |
|
|
feed in some secret entropy (32 octets/256 bits are commonly considered |
529 |
|
|
enough), for example from C</dev/random> or C</dev/urandom>, and then |
530 |
|
|
generate some key material. |
531 |
|
|
|
532 |
|
|
# create a PRNG object |
533 |
|
|
my $prng = new Crypt::Spritz::PRNG; |
534 |
|
|
|
535 |
|
|
# seed some entropy (either via ->add or in the constructor) |
536 |
|
|
$prng->add ($some_secret_highly_entropic_string); |
537 |
|
|
|
538 |
|
|
# now call get as many times as you wish to get |
539 |
|
|
# hard to guess binary randomness |
540 |
|
|
my $key1 = $prng->get (32); |
541 |
|
|
my $key2 = $prng->get (16); |
542 |
|
|
... |
543 |
|
|
|
544 |
|
|
# for long running programs, it is advisable to |
545 |
|
|
# reseed the PRNG from time to time with new entropy |
546 |
|
|
$prng->add ($some_more_entropy); |
547 |
|
|
|
548 |
|
|
=over 4 |
549 |
|
|
|
550 |
|
|
=item $prng = new Crypt::Spritz::PRNG [$seed] |
551 |
|
|
|
552 |
|
|
Creates a new random number generator object. If C<$seed> is given, then |
553 |
|
|
the C<$seed> is added to the internal state as if by a call to C<add>. |
554 |
root |
1.1 |
|
555 |
root |
1.4 |
=item $prng->add ($entropy) |
556 |
|
|
|
557 |
|
|
Adds entropy to the internal state, thereby hopefully making it harder |
558 |
|
|
to guess. Good sources for entropy are irregular hardware events, or |
559 |
|
|
randomness provided by C</dev/urandom> or C</dev/random>. |
560 |
|
|
|
561 |
|
|
The design of the Spritz PRNG should make it strong against attacks where |
562 |
|
|
the attacker controls all the entropy, so it should be safe to add entropy |
563 |
|
|
from untrusted sources - more is better than less if you need a CSPRNG. |
564 |
|
|
|
565 |
|
|
For use as PRNG, of course, this matters very little. |
566 |
|
|
|
567 |
|
|
=item $octets = $prng->get ($length) |
568 |
|
|
|
569 |
|
|
Generates and returns C<$length> random octets as a string. |
570 |
root |
1.1 |
|
571 |
|
|
=back |
572 |
|
|
|
573 |
root |
1.4 |
|
574 |
root |
1.1 |
=head1 SEE ALSO |
575 |
|
|
|
576 |
root |
1.4 |
L<http://people.csail.mit.edu/rivest/pubs/RS14.pdf>. |
577 |
root |
1.1 |
|
578 |
|
|
=head1 SECURITY CONSIDERATIONS |
579 |
|
|
|
580 |
root |
1.4 |
I also cannot give any guarantees for security, Spritz is a very new |
581 |
|
|
cryptographic algorithm, and when this module was written, almost |
582 |
|
|
completely unproven. |
583 |
root |
1.1 |
|
584 |
|
|
=head1 AUTHOR |
585 |
|
|
|
586 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
587 |
root |
1.5 |
http://software.schmorp.de/pkg/Crypt-Spritz |
588 |
root |
1.1 |
|
589 |
|
|
=cut |
590 |
|
|
|
591 |
|
|
1; |
592 |
|
|
|