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.IX Title "Crypt::Cipher::SM4 3"
.TH Crypt::Cipher::SM4 3 2026-05-12 "perl v5.42.2" "User Contributed Perl Documentation"
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.SH NAME
Crypt::Cipher::SM4 \- Symmetric cipher SM4, key size: 128 bits
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&  ### example 1
\&  use Crypt::Mode::CBC;
\&
\&  my $key = \*(Aq...\*(Aq; # length must be a valid key size for this cipher
\&  my $iv = \*(Aq...\*(Aq;  # 16 bytes
\&  my $cbc = Crypt::Mode::CBC\->new(\*(AqSM4\*(Aq);
\&  my $ciphertext = $cbc\->encrypt("secret data", $key, $iv);
\&
\&  ### example 2 (slower)
\&  use Crypt::CBC;
\&  use Crypt::Cipher::SM4;
\&
\&  my $key = \*(Aq...\*(Aq; # length must be a valid key size for this cipher
\&  my $iv = \*(Aq...\*(Aq;  # 16 bytes
\&  my $cbc = Crypt::CBC\->new( \-cipher=>\*(AqCipher::SM4\*(Aq, \-key=>$key, \-iv=>$iv );
\&  my $ciphertext = $cbc\->encrypt("secret data");
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module implements the SM4 cipher. Its interface is compatible with Crypt::CBC.
.PP
\&\fBNote:\fR This module only implements single\-block encryption and decryption.
For general data, use a block mode such as
Crypt::Mode::CBC, Crypt::Mode::CTR, or Crypt::CBC (which is slower).
.SH METHODS
.IX Header "METHODS"
Unless noted otherwise, assume \f(CW$c\fR is an existing cipher object created via
\&\f(CW\*(C`new\*(C'\fR, for example:
.PP
.Vb 1
\& my $c = Crypt::Cipher::SM4\->new($key);
.Ve
.SS new
.IX Subsection "new"
.Vb 3
\& my $c = Crypt::Cipher::SM4\->new($key);
\& #or
\& my $c = Crypt::Cipher::SM4\->new($key, $rounds);
\&
\& # $key .... [binary string] key of an accepted length (see keysize, min_keysize, max_keysize)
\& # $rounds . [integer] optional, number of rounds (if supported by the cipher; croaks on invalid value)
.Ve
.SS encrypt
.IX Subsection "encrypt"
Encrypts exactly one block of plaintext. The length of \f(CW$plaintext\fR must
equal "blocksize"; croaks otherwise. An empty string is accepted and
returned unchanged.
.PP
.Vb 1
\& my $ciphertext = $c\->encrypt($plaintext);
.Ve
.PP
Returns the encrypted block as a binary string (raw bytes).
.SS decrypt
.IX Subsection "decrypt"
Decrypts exactly one block of ciphertext. The length of \f(CW$ciphertext\fR must
equal "blocksize"; croaks otherwise. An empty string is accepted and
returned unchanged.
.PP
.Vb 1
\& my $plaintext = $c\->decrypt($ciphertext);
.Ve
.PP
Returns the decrypted block as a binary string (raw bytes).
.SS keysize
.IX Subsection "keysize"
Just an alias for \f(CW\*(C`max_keysize\*(C'\fR.
.PP
.Vb 5
\&  $c\->keysize;
\&  #or
\&  Crypt::Cipher::SM4\->keysize;
\&  #or
\&  Crypt::Cipher::SM4::keysize;
.Ve
.SS blocksize
.IX Subsection "blocksize"
Returns the cipher block size (in bytes).
.PP
.Vb 5
\&  $c\->blocksize;
\&  #or
\&  Crypt::Cipher::SM4\->blocksize;
\&  #or
\&  Crypt::Cipher::SM4::blocksize;
.Ve
.SS max_keysize
.IX Subsection "max_keysize"
Returns the maximum key size (in bytes).
.PP
.Vb 5
\&  $c\->max_keysize;
\&  #or
\&  Crypt::Cipher::SM4\->max_keysize;
\&  #or
\&  Crypt::Cipher::SM4::max_keysize;
.Ve
.SS min_keysize
.IX Subsection "min_keysize"
Returns the minimum key size (in bytes).
.PP
.Vb 5
\&  $c\->min_keysize;
\&  #or
\&  Crypt::Cipher::SM4\->min_keysize;
\&  #or
\&  Crypt::Cipher::SM4::min_keysize;
.Ve
.SS default_rounds
.IX Subsection "default_rounds"
Returns the cipher\*(Aqs default round count.
.PP
.Vb 5
\&  $c\->default_rounds;
\&  #or
\&  Crypt::Cipher::SM4\->default_rounds;
\&  #or
\&  Crypt::Cipher::SM4::default_rounds;
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP \(bu 4
CryptX, Crypt::Cipher
.IP \(bu 4
<https://en.wikipedia.org/wiki/SM4_(cipher)>