NAME

Crypt::AuthEnc::SIV - Authenticated encryption in SIV mode

SYNOPSIS

use Crypt::AuthEnc::SIV qw( siv_encrypt_authenticate siv_decrypt_verify );
my $ciphertext = siv_encrypt_authenticate('AES', $key, $plaintext);
my $ciphertext = siv_encrypt_authenticate('AES', $key, $plaintext, $adata);
my $ciphertext = siv_encrypt_authenticate('AES', $key, $plaintext, [$ad1, $ad2, ...]);
my $plaintext = siv_decrypt_verify('AES', $key, $ciphertext);
my $plaintext = siv_decrypt_verify('AES', $key, $ciphertext, $adata);
my $plaintext = siv_decrypt_verify('AES', $key, $ciphertext, [$ad1, $ad2, ...]); # undef on failure

DESCRIPTION

Since: CryptX-0.089

SIV (Synthetic IV) is a deterministic authenticated encryption scheme defined in RFC 5297 https://www.rfc-editor.org/rfc/rfc5297. Unlike nonce-based modes, SIV derives the authentication tag (the IV) synthetically from the key, associated data, and plaintext, making it nonce-misuse resistant.

The output of "siv_encrypt_authenticate" is the 16-byte SIV tag prepended to the ciphertext (total output length is "length($plaintext) + 16").

BEWARE: SIV requires a key that is twice the length of the underlying cipher key (e.g. 256 bits for AES-128-SIV, 512 bits for AES-256-SIV).

If you pass associated data as an arrayref, at most 126 components are accepted.

EXPORT

Nothing is exported by default.

You can export selected functions:

use Crypt::AuthEnc::SIV qw( siv_encrypt_authenticate siv_decrypt_verify );

FUNCTIONS

siv_encrypt_authenticate

my $ciphertext = siv_encrypt_authenticate($cipher, $key, $plaintext);
#or
my $ciphertext = siv_encrypt_authenticate($cipher, $key, $plaintext, $adata);
#or
my $ciphertext = siv_encrypt_authenticate($cipher, $key, $plaintext, [$ad1, $ad2, ...]);
# $cipher    ... [string] cipher name (e.g. 'AES')
# $key       ... [binary string] key (must be double the cipher's standard key length)
# $plaintext ... [binary string] plaintext to encrypt
# $adata     ... [binary string | arrayref] optional associated data: a scalar string or an arrayref of up to 126 string/buffer scalars

Returns a string of "length($plaintext) + 16" bytes (16-byte SIV tag prepended to ciphertext).

The required $key and $plaintext arguments must be string/buffer scalars. If $adata is given as a scalar, it must also be a string/buffer scalar. If it is given as an arrayref, each defined element must be a string/buffer scalar. String-overloaded objects are accepted.

siv_decrypt_verify

my $plaintext = siv_decrypt_verify($cipher, $key, $ciphertext);
#or
my $plaintext = siv_decrypt_verify($cipher, $key, $ciphertext, $adata);
#or
my $plaintext = siv_decrypt_verify($cipher, $key, $ciphertext, [$ad1, $ad2, ...]);
# $cipher     ... [string] cipher name (e.g. 'AES')
# $key        ... [binary string] key (must be double the cipher's standard key length)
# $ciphertext ... [binary string] ciphertext with 16-byte SIV tag prepended
# $adata      ... [binary string | arrayref] optional associated data: a scalar string or an arrayref of up to 126 string/buffer scalars

Returns the plaintext on success, or "undef" if authentication fails. Malformed ciphertext shorter than 16 bytes croaks because it cannot contain the required prepended SIV tag.

The required $key and $ciphertext arguments must be string/buffer scalars. If $adata is given as a scalar, it must also be a string/buffer scalar. If it is given as an arrayref, each defined element must be a string/buffer scalar. String-overloaded objects are accepted.