tAdd cream(5) manual page about internal format - cream - Stream encryption utility
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 (DIR) commit 97856352a98e752cfb2c1588a0c176f0fc7f0bc6
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 (HTM) Author: Willy Goiffon <contact@z3bra.org>
       Date:   Thu, 15 Sep 2022 17:58:42 +0200
       
       Add cream(5) manual page about internal format
       
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       +.Dd 2022-09-15
       +.Dt CREAM 5
       +.Os POSIX.1-2017
       +.Sh NAME
       +.Nm cream
       +.Nd Encrypted stream data format
       +.Sh DESCRIPTION
       +.Nm
       +data is the concatenation of a 16 bytes salt, and a flow of encrypted data.
       +.Pp
       +Data is encrypted with a key derivated from a
       +.Em password
       +and a 
       +.Em salt .
       +.Sh CRYPTOGRAPHY INTERNALS
       +.Ss Encryption
       +XChaCha20-Poly1305 is used to encrypt the data. It is a symetrical cipher,
       +so key used to encrypt the data must be used to decrypt it.
       +.Ss Key derivation
       +Argon2id is used to derivate the key from a password + salt combo.
       +.Pp
       +The master password must be known to both parties, and the salt is sent
       +as the first 16 bytes of the stream. This means that the receiver must
       +only know the password to decrypt the data.
       +.Sh SEE ALSO
       +.Xr cream 1
       +.Sh AUTHORS
       +.An Willy Goiffon Aq Mt dev@z3bra.org