Perl Requires Chilkat v11.6.0+

Argon2 Key Derivation with a Secret (Pepper), AD, and Encodings

Demonstrates the optional Argon2 options for Crypt2.Argon2DeriveKey: secret (a pepper), ad (associated data), the encoding member and its per-member overrides saltEncoding/secretEncoding/adEncoding, passwordCharset, and maxMemoryKb.

Background. A pepper is a secret value held by the application and not stored with the hash, so a stolen hash database cannot be attacked without it. The encoding members control how the salt, secret, and ad text are interpreted as bytes (base64 by default; utf-8 uses the characters themselves). maxMemoryKb is a guard against an unreasonable memory cost.

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use strict;
use warnings;
use Chilkat2;

my $crypt = Chilkat2::Crypt2->new;

# The password should come from a secure source rather than being hard-coded.
my $password = 'correct horse battery staple';

# Build the Argon2 options JSON, this time using the optional secret, ad, and encoding members.
#   secret         the RFC 9106 secret value K, often called a "pepper": a key held by the
#                  application and NOT stored with the hash, so a stolen hash database cannot be
#                  attacked without it.
#   ad             optional associated data X: additional non-secret data bound into the derivation.
#   encoding       how salt, secret, and ad are encoded (default base64).  Per-member overrides are
#                  saltEncoding, secretEncoding, and adEncoding.
#   passwordCharset  the charset the password is converted to before use (default utf-8).
#   maxMemoryKb    a guard (not an Argon2 parameter) refusing to allocate more than this many KB;
#                  default 2097152 (2 GB).
my $json = Chilkat2::JsonObject->new;

# The salt is provided here as hex, overriding the default base64 for just this member.
$json->UpdateString('salt', '0102030405060708090a0b0c0d0e0f10');
$json->UpdateString('saltEncoding', 'hex');

# The pepper is supplied as UTF-8 text (its own characters are the bytes).
$json->UpdateString('secret', 'application-wide-pepper');
$json->UpdateString('secretEncoding', 'utf-8');

# Associated data, supplied as UTF-8 text.
$json->UpdateString('ad', 'user-id-42');
$json->UpdateString('adEncoding', 'utf-8');

$json->UpdateString('passwordCharset', 'utf-8');
$json->UpdateInt('maxMemoryKb', 1048576);
$json->UpdateInt('keyLen', 32);

my $bdKey = Chilkat2::BinData->new;
my $success = $crypt->Argon2DeriveKey($password, $json->Emit(), $bdKey);
if (!$success) {
    print $crypt->LastErrorText, "\n";
    exit;
}

my $keyHex = $bdKey->GetEncoded('hex');
if (!$bdKey->LastMethodSuccess) {
    print $bdKey->LastErrorText, "\n";
    exit;
}

print 'Derived key: ', $keyHex, "\n";