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.IX Title "Crypt::AuthEnc::GCMSIV 3"
.TH Crypt::AuthEnc::GCMSIV 3 2026-06-18 "perl v5.42.2" "User Contributed Perl Documentation"
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.SH NAME
Crypt::AuthEnc::GCMSIV \- Authenticated encryption in AES\-GCM\-SIV mode (RFC 8452)
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use Crypt::AuthEnc::GCMSIV qw( gcm_siv_encrypt_authenticate gcm_siv_decrypt_verify );
\&
\&  my $ciphertext = gcm_siv_encrypt_authenticate(\*(AqAES\*(Aq, $key, $nonce, $adata, $plaintext);
\&  my $plaintext  = gcm_siv_decrypt_verify(\*(AqAES\*(Aq, $key, $nonce, $adata, $ciphertext); # undef on failure
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fISince: CryptX\-0.090\fR
.PP
AES\-GCM\-SIV is a nonce\-misuse\-resistant authenticated encryption scheme defined in
RFC 8452 <https://www.rfc-editor.org/rfc/rfc8452>. Reusing a nonce with the same key
no longer reveals the plaintext or the authentication key; it only reveals whether
the same (plaintext, AAD) pair was encrypted twice.
.PP
The output of \f(CW\*(C`gcm_siv_encrypt_authenticate\*(C'\fR is the ciphertext with a 16\-byte
authentication tag appended (total output length is \f(CW\*(C`length($plaintext) + 16\*(C'\fR).
.PP
GCM\-SIV is defined only for 128\-bit block ciphers (i.e. AES); the nonce must be
exactly 12 bytes long and the key must be 16 or 32 bytes (AES\-128 / AES\-256).
.SH EXPORT
.IX Header "EXPORT"
Nothing is exported by default.
.PP
You can export selected functions:
.PP
.Vb 1
\&  use Crypt::AuthEnc::GCMSIV qw( gcm_siv_encrypt_authenticate gcm_siv_decrypt_verify );
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS gcm_siv_encrypt_authenticate
.IX Subsection "gcm_siv_encrypt_authenticate"
.Vb 1
\&  my $ciphertext = gcm_siv_encrypt_authenticate($cipher, $key, $nonce, $adata, $plaintext);
\&
\&  # $cipher    ... [string] cipher name (must be \*(AqAES\*(Aq)
\&  # $key       ... [binary string] 16\- or 32\-byte key
\&  # $nonce     ... [binary string] 12\-byte nonce
\&  # $adata     ... [binary string | undef] optional associated data
\&  # $plaintext ... [binary string] plaintext to encrypt
.Ve
.PP
Returns a string of \f(CW\*(C`length($plaintext) + 16\*(C'\fR bytes: ciphertext followed by the
16\-byte authentication tag.
.PP
The required string/buffer arguments must be plain scalars; \f(CW$adata\fR may be
\&\f(CW\*(C`undef\*(C'\fR to indicate no associated data. String\-overloaded objects are accepted.
.SS gcm_siv_decrypt_verify
.IX Subsection "gcm_siv_decrypt_verify"
.Vb 1
\&  my $plaintext = gcm_siv_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext);
\&
\&  # $cipher     ... [string] cipher name (must be \*(AqAES\*(Aq)
\&  # $key        ... [binary string] 16\- or 32\-byte key
\&  # $nonce      ... [binary string] 12\-byte nonce
\&  # $adata      ... [binary string | undef] optional associated data (must match the value used during encryption)
\&  # $ciphertext ... [binary string] ciphertext with 16\-byte tag appended
.Ve
.PP
Returns the plaintext on success, or \f(CW\*(C`undef\*(C'\fR if authentication fails.
Malformed input shorter than 16 bytes croaks because it cannot contain the
required appended tag.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP \(bu 4
CryptX, Crypt::AuthEnc::GCM, Crypt::AuthEnc::SIV
.IP \(bu 4
RFC 8452 <https://www.rfc-editor.org/rfc/rfc8452>