xsec-checksig: 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/bin/xsec-checksig - from package: xml-security-c-utils

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

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