1. A method of finding set of digital data (SDD) similar to a target SDD comprising: a) receiving, into a provided memory readable and writable by a provided CPU, one or more sets of digital data which can be presented in one-dimension, each set comprising: i) data values organized in sequential addresses or at set intervals of addresses, ii) the number of data values per data point, iii) a specified starting address, and iv) a specified number of data points, called the length; b) computing a numerical similarity signature, referred to as the equivalence signature as the volume of the presentation space, and c) computing a similarity distance between any two sets of digital data as the absolute value of the difference of their equivalence signatures; and wherein, for text, binaries, audio data and other digital data that may be presented in one-dimension, computing an equivalence signature as the length of the presentation space of the normalized digital data, further comprises: (1) arranging the data values into planes with specified starting addresses and lengths of each presentation dimension for each plane wherein the i th plane consists of the set of the i th data values at each point; and (2) normalizing the data values of each plane by linearly mapping the data of each plane individually to fixed maximum and minimum values using slope-offset formulae and the like; then looping over each x-position, from the first x-position to the second to last x-position, and for each position, a) looping over each plane, b) computing the difference of the data value at said position in the plane and the data value at said position shifted by one in the x-direction in the plane and squaring the result, c) add the result from the previous step to the result from the previous roll of this inner most loop if this is not the first roll of the said inner most loop, d) upon completion of the loop over the planes, compute the square root of the result from the last roll of the inner most loop to form the result for the current roll of the loop over the x-position, with the value for the current roll of the loop over the x-position set to zero in the initial roll of said loop over the x-position, and e) upon completion of said loop over the x-position assigning the value from the loop over the x-position as the value of the equivalence signature.