feature: adding pkcs #1 v1.5 padding functions

Author: NegaScout

src/ToyPublicKeys.jl

@@ -3,6 +3,7 @@ module ToyPublicKeys
 @enum AsymetricKeyType public_key private_key
 include("utils/primes.jl")
 include("utils/random.jl")
+include("padding/pkcs_1_v1_5.jl")
 include("rsa.jl")
 export RSAKey, encrypt, decrypt
 end

src/padding/pkcs_1_v1_5.jl

@@ -0,0 +1,18 @@
+function pad(msg:: Vector{UInt8}, pad_length=32)
+    buff = rand(UInt8(1):UInt8(typemax(UInt8)), pad_length + 3)
+    buff[1] = 0
+    buff[2] = 2
+    buff[pad_length + 3] = 0
+    append!(buff, msg)
+    return buff
+end
+
+function unpad(msg:: Vector{UInt8})
+    num_of_c_chars = 3
+    start_of_padding = 3
+    if msg[1] != 0 && msg[2] != 2
+        error("Not pkcs_1_v1_5")
+    end
+    pos = findfirst(==(0), view(msg, start_of_padding:length(msg))) + num_of_c_chars
+    return view(msg, pos:length(msg))
+end

test/runtests.jl

@@ -49,4 +49,12 @@ end
     @test decrypted == msg
 end
 
+@testset "padding/pkcs_1_v1_5" begin
+    test_vector = Vector{UInt8}([1,2,3])
+    Random.seed!(42)
+    padded_vector_correct = UInt8[0x00, 0x02, 0x7a, 0xb4, 0xac, 0x2b, 0x9d, 0xab, 0x75, 0x4d, 0xa9, 0xa4, 0x58, 0x45, 0x84, 0x17, 0x46, 0x31, 0x6d, 0x7c, 0x15, 0x84, 0x33, 0x9a, 0x66, 0x51, 0x6f, 0xdb, 0x52, 0x90, 0x53, 0x29, 0xb9, 0x5f, 0x00, 0x01, 0x02, 0x03]
+    padded_vec = ToyPublicKeys.pad(test_vector)
+    @test padded_vector_correct == padded_vec
+    unpadded_vector = ToyPublicKeys.unpad(padded_vector_correct)
+    @test test_vector == unpadded_vector
 end