[arm-crypto] basic crt mode for RSA

[arm-crypto-lib.git] / rsa / rsa_basic.c

diff --git a/rsa/rsa_basic.c b/rsa/rsa_basic.c
index 3e536b8cbf78bce230a13bbb6550c4e342e50e4f..d152be2fb735e36093e81831411ad6f2f208a809 100644 (file)
--- a/rsa/rsa_basic.c
+++ b/rsa/rsa_basic.c
@@ -29,8 +29,55 @@ void rsa_enc(bigint_t* data, rsa_publickey_t* key){
        bigint_expmod_u(data, data, key->exponent, key->modulus);
 }
 
-void rsa_dec(bigint_t* data, rsa_privatekey_t* key){
-       bigint_expmod_u(data, data, key->exponent, key->modulus);
+/*
+(p,q,dp,dq,qinv)
+m1 = c**dp % p
+m2 = c**dq % q
+h = (m1 - m2) * qinv % p
+m = m2 + q * h
+*/
+
+uint8_t rsa_dec_crt_mono(bigint_t* data, rsa_privatekey_t* key){
+       bigint_t m1, m2;
+       m1.wordv = malloc(key->components[0]->length_B * sizeof(bigint_word_t));
+       m2.wordv = malloc(key->components[1]->length_B * sizeof(bigint_word_t));
+       if(!m1.wordv || !m2.wordv){
+               free(m1.wordv);
+               free(m2.wordv);
+               return 1;
+       }
+       bigint_expmod_u(&m1, data, key->components[2], key->components[0]);
+       bigint_expmod_u(&m2, data, key->components[3], key->components[1]);
+       bigint_sub_s(&m1, &m1, &m2);
+       while(BIGINT_NEG_MASK & m1.info){
+               bigint_add_s(&m1, &m1, key->components[0]);
+       }
+       bigint_reduce(&m1, key->components[0]);
+       bigint_mul_u(data, &m1, key->components[4]);
+       bigint_reduce(data, key->components[0]);
+       bigint_mul_u(data, data, key->components[1]);
+       bigint_add_u(data, data, &m2);
+       free(m1.wordv);
+       free(m2.wordv);
+       return 0;
+}
+
+uint8_t rsa_dec(bigint_t* data, rsa_privatekey_t* key){
+       if(key->n == 1){
+               bigint_expmod_u(data, data, key->components[0], key->modulus);
+               return 0;
+       }
+       if(key->n == 5){
+               if (rsa_dec_crt_mono(data, key)){
+                       return 3;
+               }
+               return 0;
+       }
+       if(key->n<8 || (key->n-5)%3 != 0){
+               return 1;
+       }
+       //rsa_dec_crt_multi(data, key, (key->n-5)/3);
+       return 2;
 }
 
 void rsa_os2ip(bigint_t* dest, const void* data, uint32_t length_B){