Xbase++ 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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LOCAL nSuccess
LOCAL oCrypt
LOCAL cPassword
LOCAL oJson
LOCAL oBdKey
LOCAL cKeyHex

nSuccess := 0

oCrypt := CreateObject("Chilkat.Crypt2")

//  The password should come from a secure source rather than being hard-coded.
cPassword := "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).
oJson := CreateObject("Chilkat.JsonObject")

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

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

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

oJson:UpdateString("passwordCharset", "utf-8")
oJson:UpdateInt("maxMemoryKb", 1048576)
oJson:UpdateInt("keyLen", 32)

oBdKey := CreateObject("Chilkat.BinData")
nSuccess := oCrypt:Argon2DeriveKey(cPassword, oJson:Emit(), oBdKey)
IF (nSuccess == 0)
    ? oCrypt:LastErrorText
    oCrypt:destroy()
    oJson:destroy()
    oBdKey:destroy()
    RETURN
ENDIF

cKeyHex := oBdKey:GetEncoded("hex")
IF (oBdKey:LastMethodSuccess == 0)
    ? oBdKey:LastErrorText
    oCrypt:destroy()
    oJson:destroy()
    oBdKey:destroy()
    RETURN
ENDIF

? "Derived key: " + cKeyHex

oCrypt:destroy()
oJson:destroy()
oBdKey:destroy()