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.IX Title "Crypt::AuthEnc::SIV 3"
.TH Crypt::AuthEnc::SIV 3 2026-05-12 "perl v5.42.2" "User Contributed Perl Documentation"
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.SH NAME
Crypt::AuthEnc::SIV \- Authenticated encryption in SIV mode
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use Crypt::AuthEnc::SIV qw( siv_encrypt_authenticate siv_decrypt_verify );
\&
\&  my $ciphertext = siv_encrypt_authenticate(\*(AqAES\*(Aq, $key, $plaintext);
\&  my $ciphertext = siv_encrypt_authenticate(\*(AqAES\*(Aq, $key, $plaintext, $adata);
\&  my $ciphertext = siv_encrypt_authenticate(\*(AqAES\*(Aq, $key, $plaintext, [$ad1, $ad2, ...]);
\&
\&  my $plaintext = siv_decrypt_verify(\*(AqAES\*(Aq, $key, $ciphertext);
\&  my $plaintext = siv_decrypt_verify(\*(AqAES\*(Aq, $key, $ciphertext, $adata);
\&  my $plaintext = siv_decrypt_verify(\*(AqAES\*(Aq, $key, $ciphertext, [$ad1, $ad2, ...]); # undef on failure
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fISince: CryptX\-0.089\fR
.PP
SIV (Synthetic IV) is a deterministic authenticated encryption scheme defined in
RFC 5297 <https://www.rfc-editor.org/rfc/rfc5297>. Unlike nonce\-based modes, SIV derives
the authentication tag (the IV) synthetically from the key, associated data, and plaintext,
making it nonce\-misuse resistant.
.PP
The output of \f(CW\*(C`siv_encrypt_authenticate\*(C'\fR is the 16\-byte SIV tag prepended to the ciphertext
(total output length is \f(CW\*(C`length($plaintext) + 16\*(C'\fR).
.PP
\&\fBBEWARE:\fR 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).
.PP
If you pass associated data as an arrayref, at most 126 components are accepted.
.SH EXPORT
.IX Header "EXPORT"
Nothing is exported by default.
.PP
You can export selected functions:
.PP
.Vb 1
\&  use Crypt::AuthEnc::SIV qw( siv_encrypt_authenticate siv_decrypt_verify );
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS siv_encrypt_authenticate
.IX Subsection "siv_encrypt_authenticate"
.Vb 5
\&  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. \*(AqAES\*(Aq)
\&  # $key       ... [binary string] key (must be double the cipher\*(Aqs standard key length)
\&  # $plaintext ... [binary string] plaintext to encrypt
\&  # $adata     ... [binary string | arrayref] optional associated data: a scalar string or an arrayref of up to 126 string/buffer scalars
.Ve
.PP
Returns a string of \f(CW\*(C`length($plaintext) + 16\*(C'\fR bytes (16\-byte SIV tag prepended to ciphertext).
.PP
The required \f(CW$key\fR and \f(CW$plaintext\fR arguments must be string/buffer scalars.
If \f(CW$adata\fR 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.
.SS siv_decrypt_verify
.IX Subsection "siv_decrypt_verify"
.Vb 5
\&  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. \*(AqAES\*(Aq)
\&  # $key        ... [binary string] key (must be double the cipher\*(Aqs standard key length)
\&  # $ciphertext ... [binary string] ciphertext with 16\-byte SIV tag prepended
\&  # $adata      ... [binary string | arrayref] optional associated data: a scalar string or an arrayref of up to 126 string/buffer scalars
.Ve
.PP
Returns the plaintext on success, or \f(CW\*(C`undef\*(C'\fR if authentication fails.
Malformed ciphertext shorter than 16 bytes croaks because it cannot contain the required
prepended SIV tag.
.PP
The required \f(CW$key\fR and \f(CW$ciphertext\fR arguments must be string/buffer
scalars. If \f(CW$adata\fR 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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP \(bu 4
CryptX, Crypt::AuthEnc::EAX, Crypt::AuthEnc::GCM
.IP \(bu 4
RFC 5297 <https://www.rfc-editor.org/rfc/rfc5297>