Document that libscrypt_check modifies mcf

1 files changed, 4 insertions, 1 deletions

diff --git a/README.md b/README.md
index 802b51f..494c8f3 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ Libscrypt's easier to use interface wraps this up to deal with the salt and prod
 
     int libscrypt_hash(char *dst, char *passphrase, uint32_t N, uint8_t r, uint8_t p);
 
-Sane constants have been created for N, r and p so you can create a has like this:
+Sane constants have been created for N, r and p so you can create a hash like this:
 
     libscrypt_hash(outbuf, "My cats's breath smells like cat food", SCRYPT_N, SCRYPT_r, SCRYPT_p);
 
@@ -35,6 +35,9 @@ Output stored in "outbuf" is stored in a standardised MCF form, which means incl
 
 mcf should be defined as at least SCRYPT_MCF_LEN in size.
 
+Note that libscrypt_check needs to modify the mcf string and will not return it
+to the original state. Pass it a copy if you need to keep the original mcf.
+
 A number of internal functions are exposed, and users wishing to create more complex use cases should consult the header file, which is aimed at documenting the API fully.
 
 The test reference is also aimed at providing a well documented use case.