Are you asking the correct question ?

How long is the hash ? 25 characters or ?

Do intruders have access to the application to decrypt then message ?

If so, it is the password that needs to be long and string.

If no access to the encrypt/decrypt app then the hash, almost any hash,
will be plenty strong.

Basically is is the length of the string used to do the encryption that
determines how difficult it will be.

Assuming you use upper case + lower case + numerics + symbols in your
long password.

Each character position of a password has many possibilities:
for my keyboard
number of alpha upper case = 26
number of alpha lower case = 26
number of symbols = 28 .,/?'";:[{]}=+-_)(*&^%$#@!~`
number of digits = 10

Calculate the permutation base on some length of password.
If I did this right, for this combination with a 10 character password.
combinations roughly = 75,330,543,424,778,800,000,000,000.
with 12
combinations roughly = 62,843,752,546,687,400,000,000,000,000,000

now if the hash is considered as being 25 characters then trying to
guess the hash: (hash is typically uppercase alpha and digits = 36
possibilities)
combinations is roughly =
144,552,334,519,691,000,000,000,000,000,000,000,00 0,000,000,000,000,000,000,000.000

Some mathematician will come along and correct me.