Lianja 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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llSuccess = .F.

loCrypt = createobject("CkCrypt2")

//  The password should come from a secure source rather than being hard-coded.
lcPassword = "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).
loJson = createobject("CkJsonObject")

//  The salt is provided here as hex, overriding the default base64 for just this member.
loJson.UpdateString("salt","0102030405060708090a0b0c0d0e0f10")
loJson.UpdateString("saltEncoding","hex")

//  The pepper is supplied as UTF-8 text (its own characters are the bytes).
loJson.UpdateString("secret","application-wide-pepper")
loJson.UpdateString("secretEncoding","utf-8")

//  Associated data, supplied as UTF-8 text.
loJson.UpdateString("ad","user-id-42")
loJson.UpdateString("adEncoding","utf-8")

loJson.UpdateString("passwordCharset","utf-8")
loJson.UpdateInt("maxMemoryKb",1048576)
loJson.UpdateInt("keyLen",32)

loBdKey = createobject("CkBinData")
llSuccess = loCrypt.Argon2DeriveKey(lcPassword,loJson.Emit(),loBdKey)
if (llSuccess = .F.) then
    ? loCrypt.LastErrorText
    release loCrypt
    release loJson
    release loBdKey
    return
endif

lcKeyHex = loBdKey.GetEncoded("hex")
if (loBdKey.LastMethodSuccess = .F.) then
    ? loBdKey.LastErrorText
    release loCrypt
    release loJson
    release loBdKey
    return
endif

? "Derived key: " + lcKeyHex


release loCrypt
release loJson
release loBdKey