ANSI_X_923.js

function ANSI_X923_pad(hex_str, blocksize) {
	blocksize = blocksize || 512; // in bits
	var bit_str_len = hex_str.length * 4; // in bits
	var bit_str_len_hex = bit_str_len.toString(16);
	
	// how many nibbles are left over?
	var pad_nibbles = (((bit_str_len / blocksize) < 1) ? (blocksize - (bit_str_len_hex.length * 4)) - bit_str_len : (blocksize - (bit_str_len_hex.length * 4)) - (bit_str_len - blocksize)) / 4;
	return hex_str + new Array(1 + pad_nibbles).join(0) + bit_str_len_hex;
}