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authorsiddharth <s@ricketyspace.net>2022-03-05 16:20:14 -0500
committersiddharth <s@ricketyspace.net>2022-03-05 16:20:14 -0500
commiteadd6510088f87b012361bfc80332cafd5af7615 (patch)
tree5a5b6d47a1907455342c89695e1d0008c1807411 /lib/sha256.go
parent86eedb619f8135adc2b457b5928367fb72f4d4b2 (diff)
lib: add sha256 implementation
Diffstat (limited to 'lib/sha256.go')
-rw-r--r--lib/sha256.go192
1 files changed, 192 insertions, 0 deletions
diff --git a/lib/sha256.go b/lib/sha256.go
new file mode 100644
index 0000000..da6dd7c
--- /dev/null
+++ b/lib/sha256.go
@@ -0,0 +1,192 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+// SHA-256 implementation.
+// Reference https://csrc.nist.gov/publications/detail/fips/180/4/final
+
+type Sha256 struct {
+ hvs []uint32
+ Msg []byte
+ MsgLen int
+}
+
+// SHA-256 Constants
+var sha256K []uint32 = []uint32{
+ 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+ 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+ 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+ 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+ 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+ 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+ 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+ 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+}
+
+// SHA-256 initial hash values.
+var sha256HashValues []uint32 = []uint32{
+ 0x6a09e667,
+ 0xbb67ae85,
+ 0x3c6ef372,
+ 0xa54ff53a,
+ 0x510e527f,
+ 0x9b05688c,
+ 0x1f83d9ab,
+ 0x5be0cd19,
+}
+
+// Ch(x,y,z) function.
+func sha256FCh(x, y, z uint32) uint32 {
+ return (x & y) ^ (^x & z)
+}
+
+// Maj(x,y,z) function.
+func sha256FMaj(x, y, z uint32) uint32 {
+ return (x & y) ^ (x & z) ^ (y & z)
+}
+
+// Σ0(x) function.
+func sha256FΣ0(x uint32) uint32 {
+ return shaRotr(x, 2) ^ shaRotr(x, 13) ^ shaRotr(x, 22)
+}
+
+// Σ1(x) function.
+func sha256FΣ1(x uint32) uint32 {
+ return shaRotr(x, 6) ^ shaRotr(x, 11) ^ shaRotr(x, 25)
+}
+
+// σ0(x) function.
+func sha256Fσ0(x uint32) uint32 {
+ return shaRotr(x, 7) ^ shaRotr(x, 18) ^ shaShr(x, 3)
+}
+
+// σ1(x) function.
+func sha256Fσ1(x uint32) uint32 {
+ return shaRotr(x, 17) ^ shaRotr(x, 19) ^ shaShr(x, 10)
+}
+
+// Returns the message schedule W_t for a message block `mb`
+// The message schedule has 64 32-bit words.
+func sha256MessageSchedule(mb []uint32) []uint32 {
+ // Message schedule.
+ w := make([]uint32, 0)
+
+ // Generate message schedule.
+ for t := 0; t < 64; t++ {
+ if t <= 15 {
+ w = append(w, mb[t])
+ } else {
+ w = append(w, shaAdd(
+ sha256Fσ1(w[t-2]),
+ w[t-7],
+ sha256Fσ0(w[t-15]),
+ w[t-16],
+ ))
+ }
+ }
+ return w
+}
+
+func (s *Sha256) Init(hvs []uint32) {
+ // Set initial hash values.
+ h := make([]uint32, 8)
+ if len(hvs) == 8 {
+ copy(h, hvs)
+ s.hvs = h
+ } else {
+ copy(h, sha256HashValues)
+ s.hvs = h
+ }
+}
+
+func (s *Sha256) Message(m []byte) {
+ s.Msg = m
+ s.MsgLen = len(m)
+}
+
+// SHA-256 - Pad message such that its length is a multiple of 512.
+func (s *Sha256) Pad() []byte {
+ // Initialize padded message.
+ pm := make([]byte, len(s.Msg))
+ copy(pm, s.Msg)
+
+ // Add padding.
+ pm = append(pm, MDPadding(s.MsgLen)...)
+
+ return pm
+}
+
+func (s *Sha256) Hash() []byte {
+ // Pad message.
+ pm := s.Pad()
+
+ // Break int message blocks.
+ mbs := shaMessageBlocks(pm)
+
+ // Initialize hash values.
+ hvs := make([]uint32, 8)
+ copy(hvs, s.hvs) // Initial hash values.
+
+ // Process each message block.
+ for _, mb := range mbs {
+ // Get message schedule.
+ w := sha256MessageSchedule(mb)
+
+ // Initialize working variables.
+ a := hvs[0]
+ b := hvs[1]
+ c := hvs[2]
+ d := hvs[3]
+ e := hvs[4]
+ f := hvs[5]
+ g := hvs[6]
+ h := hvs[7]
+
+ for t := 0; t <= 63; t++ {
+ t1 := shaAdd(
+ h,
+ sha256FΣ1(e),
+ sha256FCh(e, f, g),
+ sha256K[t],
+ w[t],
+ )
+ t2 := shaAdd(sha256FΣ0(a), sha256FMaj(a, b, c))
+ h = g
+ g = f
+ f = e
+ e = shaAdd(d, t1)
+ d = c
+ c = b
+ b = a
+ a = shaAdd(t1, t2)
+ }
+
+ // Compute intermediate hash values.
+ hvs[0] = shaAdd(a, hvs[0])
+ hvs[1] = shaAdd(b, hvs[1])
+ hvs[2] = shaAdd(c, hvs[2])
+ hvs[3] = shaAdd(d, hvs[3])
+ hvs[4] = shaAdd(e, hvs[4])
+ hvs[5] = shaAdd(f, hvs[5])
+ hvs[6] = shaAdd(g, hvs[6])
+ hvs[7] = shaAdd(h, hvs[7])
+ }
+
+ // Slurp sha256 digest from hash values.
+ d := make([]byte, 0) // sha256 digest
+ for i := 0; i < 8; i++ {
+ // Break 32-bit hash value into 4 bytes.
+ hb := make([]byte, 4)
+ for j := 3; j >= 0; j-- {
+ // Get last 8 bits.
+ hb[j] = byte(hvs[i] & 0xFF)
+
+ // Get rid of last 8 bits.
+ hvs[i] = hvs[i] >> 8
+ }
+ d = append(d, hb...)
+ }
+
+ return d
+}