diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/aes.go | 23 |
1 files changed, 23 insertions, 0 deletions
@@ -3,6 +3,29 @@ package lib +// Generates counter function for AES CTR mode. +func AESGenCTRFunc(nonce uint64) func() []byte { + ctr := uint64(0) // Counter + ff := uint64(0xFF) + cf := func() []byte { + cb := make([]byte, 16) // counter block + var i, j uint + // Put nonce in the first 8 bytes in cb in little endian format + for i = 0; i < 8; i++ { + n := nonce & (ff << (i * 8)) // Reset all except the i^th byte of the nonce + cb[i] = byte(n >> (i * 8)) // Retrieve i^th byte of the nonce + } + // Put counter in the next 8 bytes in cb in little endian format + for i, j = 8, 0; i < 16; i, j = i+1, j+1 { + n := ctr & (ff << (j * 8)) // Reset all except the j^th byte of the counter + cb[i] = byte(n >> (j * 8)) // Retrieve j^th byte of the counter + } + ctr += 1 // Increment counter by 1 + return cb + } + return cf +} + func AESEncryptCTR(plain, key []byte, ctrFunc func() []byte) ([]byte, error) { if len(key) != 16 { return []byte{}, CPError{"key length != 16"} |