You could parse the file with awk:
awk ' /^[[:alnum:]]*:/ { user=substr($0, 1, index($0, ":") - 1) } /^ *password *=/ { split($0, elements, " *= *"); print user ":" elements[2] }' \ /etc/security/passwd
The idea behind the script is to first find the username line -- one starting with and containing alphanumeric characters, followed by a colon -- and extract that username with the "substr" function. On lines that start with zero or more spaces followed by the string "password", followed by zero or more spaces and an equals-sign, we split the line across the equals-sign and print the saved username with the password portion of the current line.