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.\"
.IX Title "Crypt::AuthEnc::CCM 3pm"
.TH Crypt::AuthEnc::CCM 3pm 2024-03-07 "perl v5.38.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
Crypt::AuthEnc::CCM \- Authenticated encryption in CCM mode
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\& ### OO interface
\& use Crypt::AuthEnc::CCM;
\&
\& # encrypt and authenticate
\& my $ae = Crypt::AuthEnc::CCM\->new("AES", $key, $iv, $adata, $tag_len, $pt_len);
\& my $ct = $ae\->encrypt_add(\*(Aqdata1\*(Aq);
\& $ct .= $ae\->encrypt_add(\*(Aqdata2\*(Aq);
\& $ct .= $ae\->encrypt_add(\*(Aqdata3\*(Aq);
\& my $tag = $ae\->encrypt_done();
\&
\& # decrypt and verify
\& my $ae = Crypt::AuthEnc::CCM\->new("AES", $key, $iv, $adata, $tag_len, $pt_len);
\& my $pt = $ae\->decrypt_add(\*(Aqciphertext1\*(Aq);
\& $pt .= $ae\->decrypt_add(\*(Aqciphertext2\*(Aq);
\& $pt .= $ae\->decrypt_add(\*(Aqciphertext3\*(Aq);
\& my $tag = $ae\->decrypt_done();
\& die "decrypt failed" unless $tag eq $expected_tag;
\&
\& #or
\& my $result = $ae\->decrypt_done($expected_tag); # 0 or 1
\&
\& ### functional interface
\& use Crypt::AuthEnc::CCM qw(ccm_encrypt_authenticate ccm_decrypt_verify);
\&
\& ($ciphertext, $tag) = ccm_encrypt_authenticate(\*(AqAES\*(Aq, $key, $nonce, $adata, $tag_len, $plaintext);
\& $plaintext = ccm_decrypt_verify(\*(AqAES\*(Aq, $key, $nonce, $adata, $ciphertext, $tag);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
CCM is a encrypt+authenticate mode that is centered around using AES (or any 16\-byte cipher) as a primitive.
Unlike EAX and OCB mode, it is only meant for packet mode where the length of the input is known in advance.
.SH EXPORT
.IX Header "EXPORT"
Nothing is exported by default.
.PP
You can export selected functions:
.PP
.Vb 1
\& use Crypt::AuthEnc::CCM qw(ccm_encrypt_authenticate ccm_decrypt_verify);
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS ccm_encrypt_authenticate
.IX Subsection "ccm_encrypt_authenticate"
.Vb 1
\& my ($ciphertext, $tag) = ccm_encrypt_authenticate($cipher, $key, $nonce, $adata, $tag_len, $plaintext);
\&
\& # $cipher .. \*(AqAES\*(Aq or name of any other cipher with 16\-byte block len
\& # $key ..... key of proper length (e.g. 128/192/256bits for AES)
\& # $nonce ... unique nonce/salt (no need to keep it secret)
\& # $adata ... additional authenticated data
\& # $tag_len . required length of output tag
.Ve
.PP
CCM parameters should follow <http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800\-38c.pdf>
.PP
.Vb 3
\& # tag length:   4, 6, 8, 10, 12, 14, 16 (reasonable minimum is 8)
\& # nonce length: 7, 8, 9, 10, 11, 12, 13 (if you are not sure, use 11)
\& # BEWARE nonce length determines max. enc/dec data size: max_data_size = 2^(8*(15\-nonce_len))
.Ve
.SS ccm_decrypt_verify
.IX Subsection "ccm_decrypt_verify"
.Vb 2
\& my $plaintext = ccm_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
\& # on error returns undef
.Ve
.SH METHODS
.IX Header "METHODS"
.SS new
.IX Subsection "new"
.Vb 1
\& my $ae = Crypt::AuthEnc::CCM\->new($cipher, $key, $nonce, $adata, $tag_len, $pt_len);
\&
\& # $cipher .. \*(AqAES\*(Aq or name of any other cipher with 16\-byte block len
\& # $key ..... key of proper length (e.g. 128/192/256bits for AES)
\& # $nonce ... unique nonce/salt (no need to keep it secret)
\& # $adata ... additional authenticated data
\& # $tag_len . required length of output tag
\& # $pt_len .. expected length of plaintext/ciphertext to encrypt/decrypt
.Ve
.SS encrypt_add
.IX Subsection "encrypt_add"
.Vb 1
\& $ciphertext = $ae\->encrypt_add($data);        # can be called multiple times
.Ve
.SS encrypt_done
.IX Subsection "encrypt_done"
.Vb 1
\& my $tag = $ae\->encrypt_done;                  # returns $tag value
.Ve
.SS decrypt_add
.IX Subsection "decrypt_add"
.Vb 1
\& $plaintext = $ae\->decrypt_add($ciphertext);   # can be called multiple times
.Ve
.SS decrypt_done
.IX Subsection "decrypt_done"
.Vb 3
\& my $tag = $ae\->decrypt_done;           # returns $tag value
\& #or
\& my $result = $ae\->decrypt_done($tag);  # returns 1 (success) or 0 (failure)
.Ve
.SS clone
.IX Subsection "clone"
.Vb 1
\& my $ae_new = $ae\->clone;
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP \(bu 4
CryptX, Crypt::AuthEnc::EAX, Crypt::AuthEnc::GCM, Crypt::AuthEnc::OCB
.IP \(bu 4
<https://en.wikipedia.org/wiki/CCM_mode>