SHA-1 Algorithm


The SHA-1 secure hash algorithm is a hash-based cryptographic function, it takes a message of arbitrary length as its input, produces a 160-bit digest. It has a padding and appending process before digest the message of arbitrary length.

The SHA-1 algorithm is defined in FIPS 180.

Implementation on FPGA

The internal structure of SHA-1 is shown in the figure below:

Structure of SHA-1

As we can see from the figures, the hash calculation can be partitioned into two parts.

  • The pre-processing part pads or splits the input message which is comprised by a stream of 32-bit words into fixed sized blocks (512-bit for each).
  • The digest part iteratively computes the hash values. Loop-carried dependency is enforced by the algorithm itself, thus this part cannot reach an initiation interval (II) = 1.

As the two parts can work independently, they are designed into parallel dataflow process, connected by streams (FIFOs).


A single instance of SHA-1 function processes input message at the rate of 512 bit / 84 cycles at 346.62MHz.

The hardware resource utilizations are listed in tab1SHA1 below:

Hardware resources for single SHA-1 hash calculation
BRAM DSP FF LUT CLB SRL clock period(ns)
1 0 7518 3633 976 0 3.004