cipher_driver: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/srtp/bin/cipher_driver - from package: srtp-utils

You may install the required package with command apt-get install {package}

Error in other languages:
cipher_driver: bevel nie gevind nie
cipher_driver: comandă negăsită
cipher_driver: comando não encontrado
cipher_driver: commande introuvable
cipher_driver: command not found
cipher_driver: käsku ei ole
cipher_driver: không tìm thấy lệnh
cipher_driver: komanda nerasta
cipher_driver: Kommando nicht gefunden.
cipher_driver: kommandot finns inte
cipher_driver: komut yok
cipher_driver: nie znaleziono polecenia
cipher_driver: níor aimsíodh an t-ordú
cipher_driver: no se encontró la orden
cipher_driver: no s'ha trobat l'ordre
cipher_driver: opdracht niet gevonden
cipher_driver: parancs nem található
cipher_driver: perintah tidak ditemukan
cipher_driver: príkaz nenájdený
cipher_driver: příkaz nenalezen
cipher_driver: команда не найдена
cipher_driver: командата не е открита
cipher_driver: 命令找不到
cipher_driver: コマンドが見つかりません