Self-adjusting key decoder comprising a handle for a decoder and a working blade for a decoder, which handle for a decoder comprises a manipulator of a pumper and a fixed handle, wherein a cylindrical portion of the manipulator of a pumper is located coaxially and at least partially in a cylindrical channel with two opposite holes, on a first side of the fixed handle, which cylindrical channel is located along the entire length of the fixed handle, and extends to a second side of the fixed handle, wherein the fixed handle has at least one side hole for fixed attachment to the working blade, and the working blade for a decoder comprises a carrier, which is an elongated element with a longitudinal channel for working details, in which a lifter and a pumper are placed parallel to each other, which are mounted with the ability for reciprocating motion relative to the carrier and relative to each other, in a direction parallel to the extension of the carrier, and characterized in that a guide bushing having a cylindrical shape is placed in the cylindrical channel of the cylindrical part of the manipulator of a pumper, wherein the manipulator of a pumper and the guide bushing are connected to each other, wherein the guide bushing has a channel located centrally along its axis to receive a working blade, wherein at least one linear channel and at least one L-shaped channel with a short side and a long side are formed on the surrounding wall of the guide bushing and subsequently arranged along the axis of the guide bushing for connecting with the working blade subsequently, wherein the at least one linear channel is located transversely to the axis of the guide bushing, at an angle to its base, wherein the short side of the at least one L-shaped channel is arranged parallel to the base of the guide bushing, and the long side of the L-shaped channel is arranged parallel to the axis of the guide bushing, wherein the carrier comprises, subsequently arranged subsequently a cylindrical part and a flat part, wherein a first through hole in which a spring is placed, a second through hole, a longitudinal linear hole and a third hole for connection with fastening elements and first and second dowels (15, 32) to a handle for a decoder are located subsequently, laterally and longitudinally on the cylindrical part, the longitudinal linear hole is formed parallel to the axis of the cylindrical part of the carrier, wherein the longitudinal channel for working details is formed on the flat part of the carrier, and also extends into the cylindrical part of the carrier and connects with the through holes (18, 19, 20) of the cylindrical part, wherein the pumper is located in the longitudinal channel with the ability for reciprocating motion along the extension of the carrier and has two end positions, respectively rear end position, where the pumper is maximally retracted into the carrier and is positioned to exert pressure on the spring with first end, and front end position where the pumper is pushed by the spring and extends maximally forward, wherein the lifter is an elongated element, with a hole at one end, by which it is fixed with the second dowel to the longitudinal linear hole of the carrier, wherein the manipulator of a pumper with the guide bushing are designed and mounted with the ability to perform two types of motions relative to the carrier, respectively reciprocating motion longitudinally to the axis of the handle and rotary motion, wherein the reciprocating motion is carried out by the motion of the first dowel in the long side of the at least one L-shaped channel of the guide bushing, and the rotary motion is performed by motion of the first dowel in the short side of the at least one L-shaped channel of the guide bushing, simultaneously with motion of the second dowel in the at least one linear channel, wherein the carrier of the working blade is placed partially in the guide bushing, and is fixed to it by means of fasteners with a possibility for transforming the rotary motion of the manipulator of a pumper into reciprocating motion of the pumper relative to the hole of the fixed handle and the carrier, respectively, the second through hole of the carrier and the at least one L-shaped channel of the guide bushing are connected by the first dowel mounted in the at least one L-shaped channel with the ability for reciprocating motion both along the long side and along the short side of the at least one L-shaped channel, and the at least one linear channel of the guide bushing, the longitudinal linear hole of the carrier, an intermediate groove of the pumper, and the hole of the lifter are connected by the second dowel mounted with the ability to move along both the longitudinal linear hole of the carrier and along the transverse linear channel of the guide bushing, wherein the carrier is immovably connected to the fixed handle by means of a fastener in a coaxially located third hole of the carrier and hole of the fixed handle, wherein at least three elongate sockets, which are parallel to each other, and which house pins under tension, are arranged in the region of the flat part of the working blade, wherein the pumper is configured to interact with the pins to carry out encoding.