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.\" ========================================================================
.\"
.IX Title "Crypt::AuthEnc::OCB 3"
.TH Crypt::AuthEnc::OCB 3 2024-10-20 "perl v5.40.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
Crypt::AuthEnc::OCB \- Authenticated encryption in OCBv3 mode
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\& ### OO interface
\& use Crypt::AuthEnc::OCB;
\&
\& # encrypt and authenticate
\& my $ae = Crypt::AuthEnc::OCB\->new("AES", $key, $nonce, $tag_len);
\& $ae\->adata_add(\*(Aqadditional_authenticated_data1\*(Aq);
\& $ae\->adata_add(\*(Aqadditional_authenticated_data2\*(Aq);
\& my $ct = $ae\->encrypt_add(\*(Aqdata1\*(Aq);
\& $ct .= $ae\->encrypt_add(\*(Aqdata2\*(Aq);
\& $ct .= $ae\->encrypt_add(\*(Aqdata3\*(Aq);
\& $ct .= $ae\->encrypt_last(\*(Aqrest of data\*(Aq);
\& my $tag = $ae\->encrypt_done();
\&
\& # decrypt and verify
\& my $ae = Crypt::AuthEnc::OCB\->new("AES", $key, $nonce, $tag_len);
\& $ae\->adata_add(\*(Aqadditional_authenticated_data1\*(Aq);
\& $ae\->adata_add(\*(Aqadditional_authenticated_data2\*(Aq);
\& my $pt = $ae\->decrypt_add(\*(Aqciphertext1\*(Aq);
\& $pt .= $ae\->decrypt_add(\*(Aqciphertext2\*(Aq);
\& $pt .= $ae\->decrypt_add(\*(Aqciphertext3\*(Aq);
\& $pt .= $ae\->decrypt_last(\*(Aqrest of data\*(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::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);
\&
\& my ($ciphertext, $tag) = ocb_encrypt_authenticate(\*(AqAES\*(Aq, $key, $nonce, $adata, $tag_len, $plaintext);
\& my $plaintext = ocb_decrypt_verify(\*(AqAES\*(Aq, $key, $nonce, $adata, $ciphertext, $tag);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module implements OCB v3 according to <https://tools.ietf.org/html/rfc7253>
.SH EXPORT
.IX Header "EXPORT"
Nothing is exported by default.
.PP
You can export selected functions:
.PP
.Vb 1
\&  use Crypt::AuthEnc::OCB qw(ocb_encrypt_authenticate ocb_decrypt_verify);
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS ocb_encrypt_authenticate
.IX Subsection "ocb_encrypt_authenticate"
.Vb 1
\& my ($ciphertext, $tag) = ocb_encrypt_authenticate($cipher, $key, $nonce, $adata, $tag_len, $plaintext);
\&
\& # $cipher .. \*(AqAES\*(Aq or name of any other cipher with 16\-byte block len
\& # $key ..... AES key of proper length (128/192/256bits)
\& # $nonce ... unique nonce/salt (no need to keep it secret)
\& # $adata ... additional authenticated data
\& # $tag_len . required length of output tag
.Ve
.SS ocb_decrypt_verify
.IX Subsection "ocb_decrypt_verify"
.Vb 2
\&  my $plaintext = ocb_decrypt_verify($cipher, $key, $nonce, $adata, $ciphertext, $tag);
\&  # on error returns undef
.Ve
.SH METHODS
.IX Header "METHODS"
.SS new
.IX Subsection "new"
.Vb 1
\& my $ae = Crypt::AuthEnc::OCB\->new($cipher, $key, $nonce, $tag_len);
\&
\& # $cipher .. \*(AqAES\*(Aq or name of any other cipher with 16\-byte block len
\& # $key ..... AES key of proper length (128/192/256bits)
\& # $nonce ... unique nonce/salt (no need to keep it secret)
\& # $tag_len . required length of output tag
.Ve
.SS adata_add
.IX Subsection "adata_add"
.Vb 1
\& $ae\->adata_add($adata);                        #can be called multiple times
.Ve
.SS encrypt_add
.IX Subsection "encrypt_add"
.Vb 1
\& $ciphertext = $ae\->encrypt_add($data);         # can be called multiple times
\&
\& #BEWARE: size of $data has to be multiple of blocklen (16 for AES)
.Ve
.SS encrypt_last
.IX Subsection "encrypt_last"
.Vb 1
\& $ciphertext = $ae\->encrypt_last($data);
.Ve
.SS encrypt_done
.IX Subsection "encrypt_done"
.Vb 1
\& $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
\&
\& #BEWARE: size of $ciphertext has to be multiple of blocklen (16 for AES)
.Ve
.SS decrypt_last
.IX Subsection "decrypt_last"
.Vb 1
\& $plaintext = $ae\->decrypt_last($data);
.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::CCM, Crypt::AuthEnc::GCM, Crypt::AuthEnc::EAX
.IP \(bu 4
<https://en.wikipedia.org/wiki/OCB_mode>
.IP \(bu 4
<https://tools.ietf.org/html/rfc7253>