slip-0039: update passphrase image

slip-0039.md

@@ -74,10 +74,10 @@ For the checksums we use the leftmost 16 bits of a SHA-256 hash digest of the re
 
 When enough M secrets are provided the master secret is reconstructed. To allow an additional protection of the final seed using a passphrase we suggest a following scenario. The passphrase is stretched using a key derivation function. Output is used as an encryption key passed to a symmetric-key cipher. The result of this encryption is the final seed to be used. If no passphrase is provided the passphrase is set to an empty string.
 
-![passphrase](slip-0039/passphrase.png)
-
 This mechanism is intentionally symmetric to allow reconstructing the master secret from the seed in case the passphrase is known.
 
+![passphrase](slip-0039/passphrase.png)
+
 We will use PBKDF2 (PRF = HMAC-SHA256, Salt = "SLIP0039", iterations = 100000, dkLen = 256 bits) as the key derivation function and ChaCha20 as the symmetric-key cipher.
 
 ## Versioning
@@ -97,6 +97,10 @@ Wordlist mandated by this SLIP is [available here](slip-0039/wordlist.txt). Seve
 * no word is shorter than 4 letters and longer than 8 letters
 * all words have unique 4-letter prefix
 
+## Test Vectors
+
+TBD
+
 ## References
 
 * [Secret Sharing Step by Step by Point Software](http://www.pointsoftware.ch/en/secret-sharing-step-by-step/)