seccure-signcrypt: command not found

Have You tried accessing the binary with the full path?

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/seccure-signcrypt - from package: seccure

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